Update md.h

Minor documentation improvements:
*Standardized file brief description.
*Separated return statements.
*Reordered tags within documentation blocks so that params and returns are last in block.
diff --git a/include/mbedtls/md.h b/include/mbedtls/md.h
index 06538c3..df2ab63 100644
--- a/include/mbedtls/md.h
+++ b/include/mbedtls/md.h
@@ -1,7 +1,7 @@
  /**
  * \file md.h
  *
- * \brief The generic message-digest wrapper.
+ * \brief This file contains the generic message-digest wrapper.
  *
  * \author Adriaan de Jong <dejong@fox-it.com>
  */
@@ -46,7 +46,7 @@
 #endif
 
 /**
- * \brief     Enumeration of supported message digests
+ * \brief     Supported message digests.
  *
  * \warning   MD2, MD4, MD5 and SHA-1 are considered weak message digests and
  *            their use constitutes a security risk. We recommend considering
@@ -54,16 +54,16 @@
  *
  */
 typedef enum {
-    MBEDTLS_MD_NONE=0,
-    MBEDTLS_MD_MD2,
-    MBEDTLS_MD_MD4,
-    MBEDTLS_MD_MD5,
-    MBEDTLS_MD_SHA1,
-    MBEDTLS_MD_SHA224,
-    MBEDTLS_MD_SHA256,
-    MBEDTLS_MD_SHA384,
-    MBEDTLS_MD_SHA512,
-    MBEDTLS_MD_RIPEMD160,
+    MBEDTLS_MD_NONE=0, /**< None. */
+    MBEDTLS_MD_MD2, /**< The MD2 message digest. */
+    MBEDTLS_MD_MD4, /**< The MD4 message digest. */
+    MBEDTLS_MD_MD5, /**< The MD5 message digest. */
+    MBEDTLS_MD_SHA1, /**< The SHA-1 message digest. */
+    MBEDTLS_MD_SHA224, /**< The SHA-224 message digest. */
+    MBEDTLS_MD_SHA256, /**< The SHA-256 message digest. */
+    MBEDTLS_MD_SHA384, /**< The SHA-384 message digest. */
+    MBEDTLS_MD_SHA512,  /**< The SHA-512 message digest. */
+    MBEDTLS_MD_RIPEMD160, /**< The RIPEMD-160 message digest. */
 } mbedtls_md_type_t;
 
 #if defined(MBEDTLS_SHA512_C)
@@ -119,8 +119,8 @@
  *
  * \param md_type   The type of digest to search for.
  *
- * \return          The message-digest information associated with \p md_type,
- *                  or NULL if not found.
+ * \return          The message-digest information associated with \p md_type.
+ * \return          NULL if the associated message-digest information is not found.
  */
 const mbedtls_md_info_t *mbedtls_md_info_from_type( mbedtls_md_type_t md_type );
 
@@ -168,9 +168,9 @@
  * \param md_info   The information structure of the message-digest algorithm
  *                  to use.
  *
- * \returns         \c 0 on success,
- *                  #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter failure,
- *                  #MBEDTLS_ERR_MD_ALLOC_FAILED memory allocation failure.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter failure.
+ * \returns         #MBEDTLS_ERR_MD_ALLOC_FAILED memory allocation failure.
  */
 int mbedtls_md_init_ctx( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info ) MBEDTLS_DEPRECATED;
 #undef MBEDTLS_DEPRECATED
@@ -187,12 +187,12 @@
  * \param ctx       The context to set up.
  * \param md_info   The information structure of the message-digest algorithm
  *                  to use.
- * \param hmac      <ul><li>0: HMAC is not used. Saves some memory.</li>
- *                  <li>non-zero: HMAC is used with this context.</li></ul>
+ * \param hmac      Defines if HMAC is used. 0: HMAC is not used (saves some memory),
+ *                  or non-zero: HMAC is used with this context.
  *
- * \returns         \c 0 on success,
- *                  #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter failure, or
- *                  #MBEDTLS_ERR_MD_ALLOC_FAILED on memory allocation failure.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter failure.
+ * \returns         #MBEDTLS_ERR_MD_ALLOC_FAILED on memory allocation failure.
  */
 int mbedtls_md_setup( mbedtls_md_context_t *ctx, const mbedtls_md_info_t *md_info, int hmac );
 
@@ -212,8 +212,8 @@
  * \param dst       The destination context.
  * \param src       The context to be cloned.
  *
- * \return          \c 0 on success,
- *                  #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter failure.
+ * \return          \c 0 on success.
+ * \return          #MBEDTLS_ERR_MD_BAD_INPUT_DATA on parameter failure.
  */
 int mbedtls_md_clone( mbedtls_md_context_t *dst,
                       const mbedtls_md_context_t *src );
@@ -260,8 +260,9 @@
  *
  * \param ctx       The generic message-digest context.
  *
- * \returns         \c 0 on success, #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_starts( mbedtls_md_context_t *ctx );
 
@@ -277,8 +278,9 @@
  * \param input     The buffer holding the input data.
  * \param ilen      The length of the input data.
  *
- * \returns         \c 0 on success, #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_update( mbedtls_md_context_t *ctx, const unsigned char *input, size_t ilen );
 
@@ -296,8 +298,9 @@
  * \param ctx       The generic message-digest context.
  * \param output    The buffer for the generic message-digest checksum result.
  *
- * \returns         \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_finish( mbedtls_md_context_t *ctx, unsigned char *output );
 
@@ -315,8 +318,9 @@
  * \param ilen     The length of the input data.
  * \param output   The generic message-digest checksum result.
  *
- * \returns        \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                 parameter verification fails.
+ * \returns        \c 0 on success.
+ * \returns        #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                 fails.
  */
 int mbedtls_md( const mbedtls_md_info_t *md_info, const unsigned char *input, size_t ilen,
         unsigned char *output );
@@ -334,9 +338,9 @@
  * \param path     The input file name.
  * \param output   The generic message-digest checksum result.
  *
- * \return         \c 0 on success,
- *                 #MBEDTLS_ERR_MD_FILE_IO_ERROR if file input failed, or
- *                 #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info was NULL.
+ * \return         \c 0 on success.
+ * \returns        #MBEDTLS_ERR_MD_FILE_IO_ERROR if file input failed.
+ * \returns        #MBEDTLS_ERR_MD_BAD_INPUT_DATA if \p md_info was NULL.
  */
 int mbedtls_md_file( const mbedtls_md_info_t *md_info, const char *path,
                      unsigned char *output );
@@ -356,8 +360,9 @@
  * \param key       The HMAC secret key.
  * \param keylen    The length of the HMAC key in Bytes.
  *
- * \returns         \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_hmac_starts( mbedtls_md_context_t *ctx, const unsigned char *key,
                     size_t keylen );
@@ -377,8 +382,9 @@
  * \param input     The buffer holding the input data.
  * \param ilen      The length of the input data.
  *
- * \returns         \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_hmac_update( mbedtls_md_context_t *ctx, const unsigned char *input,
                     size_t ilen );
@@ -397,8 +403,9 @@
  *                  context.
  * \param output    The generic HMAC checksum result.
  *
- * \returns         \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_hmac_finish( mbedtls_md_context_t *ctx, unsigned char *output);
 
@@ -413,8 +420,9 @@
  * \param ctx       The message digest context containing an embedded HMAC
  *                  context.
  *
- * \returns         \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                  parameter verification fails.
+ * \returns         \c 0 on success.
+ * \returns         #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                  fails.
  */
 int mbedtls_md_hmac_reset( mbedtls_md_context_t *ctx );
 
@@ -436,8 +444,9 @@
  * \param ilen     The length of the input data.
  * \param output   The generic HMAC result.
  *
- * \returns        \c 0 on success, or #MBEDTLS_ERR_MD_BAD_INPUT_DATA if
- *                 parameter verification fails.
+ * \returns        \c 0 on success.
+ * \returns        #MBEDTLS_ERR_MD_BAD_INPUT_DATA if parameter verification
+ *                 fails.
  */
 int mbedtls_md_hmac( const mbedtls_md_info_t *md_info, const unsigned char *key, size_t keylen,
                 const unsigned char *input, size_t ilen,