Add pk_rsa_set_padding() and rsa_set_padding()
diff --git a/include/polarssl/rsa.h b/include/polarssl/rsa.h
index 504dde2..47315a3 100644
--- a/include/polarssl/rsa.h
+++ b/include/polarssl/rsa.h
@@ -125,7 +125,24 @@
  */
 void rsa_init( rsa_context *ctx,
                int padding,
-               int hash_id);
+               int hash_id );
+
+/**
+ * \brief          Set the padding method on an initilized RSA context.
+ *
+ *                 Note: Set padding to RSA_PKCS_V21 for the RSAES-OAEP
+ *                 encryption scheme and the RSASSA-PSS signature scheme.
+ *
+ * \param ctx      RSA context to be set
+ * \param padding  RSA_PKCS_V15 or RSA_PKCS_V21
+ * \param hash_id  RSA_PKCS_V21 hash identifier
+ *
+ * \note           The hash_id parameter is actually ignored
+ *                 when using RSA_PKCS_V15 padding.
+ */
+void rsa_set_padding( rsa_context *ctx,
+                      int padding,
+                      int hash_id );
 
 /**
  * \brief          Generate an RSA keypair