Import mbedtls-2.16.0

Imports mbedTLS 2.16.0 from https://github.com/ARMmbed/mbedtls.git
commit fb1972db23da ("Merge pull request #544 from ARMmbed/version-2.16")
(tag mbedtls-2.16.0).

Certain files will never be needed and are thus removed (reducing number
of lines to almost 50%):
rm -f circle.yml CMakeLists.txt DartConfiguration.tcl Makefile
rm -f .gitignore .travis.yml .pylint
rm -f include/.gitignore include/CMakeLists.txt library/.gitignore
rm -f library/CMakeLists.txt library/Makefile
rm -rf .git .github doxygen configs programs scripts tests visualc yotta

This is a complete overwrite of previous code so earlier changes in the
branch import/mbedtls-2.6.1 will be added on top of this commit to bring
the changes forward.

Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/lib/libmbedtls/mbedtls/library/x509_csr.c b/lib/libmbedtls/mbedtls/library/x509_csr.c
index aefc6db..f844257 100644
--- a/lib/libmbedtls/mbedtls/library/x509_csr.c
+++ b/lib/libmbedtls/mbedtls/library/x509_csr.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  X.509 Certificate Signing Request (CSR) parsing
  *
  *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
  *
  *  Licensed under the Apache License, Version 2.0 (the "License"); you may
  *  not use this file except in compliance with the License.
@@ -39,6 +39,7 @@
 
 #include "mbedtls/x509_csr.h"
 #include "mbedtls/oid.h"
+#include "mbedtls/platform_util.h"
 
 #include <string.h>
 
@@ -60,11 +61,6 @@
 #include <stdio.h>
 #endif
 
-/* Implementation that should never be optimized out by the compiler */
-static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
-}
-
 /*
  *  Version  ::=  INTEGER  {  v1(0)  }
  */
@@ -278,34 +274,25 @@
         return( MBEDTLS_ERR_X509_BAD_INPUT_DATA );
 
 #if defined(MBEDTLS_PEM_PARSE_C)
-    mbedtls_pem_init( &pem );
-
     /* Avoid calling mbedtls_pem_read_buffer() on non-null-terminated string */
-    if( buf[buflen - 1] != '\0' )
-        ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
-    else
+    if( buf[buflen - 1] == '\0' )
+    {
+        mbedtls_pem_init( &pem );
         ret = mbedtls_pem_read_buffer( &pem,
                                "-----BEGIN CERTIFICATE REQUEST-----",
                                "-----END CERTIFICATE REQUEST-----",
                                buf, NULL, 0, &use_len );
 
-    if( ret == 0 )
-    {
-        /*
-         * Was PEM encoded, parse the result
-         */
-        if( ( ret = mbedtls_x509_csr_parse_der( csr, pem.buf, pem.buflen ) ) != 0 )
-            return( ret );
+        if( ret == 0 )
+            /*
+             * Was PEM encoded, parse the result
+             */
+            ret = mbedtls_x509_csr_parse_der( csr, pem.buf, pem.buflen );
 
         mbedtls_pem_free( &pem );
-        return( 0 );
+        if( ret != MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
+            return( ret );
     }
-    else if( ret != MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT )
-    {
-        mbedtls_pem_free( &pem );
-        return( ret );
-    }
-    else
 #endif /* MBEDTLS_PEM_PARSE_C */
     return( mbedtls_x509_csr_parse_der( csr, buf, buflen ) );
 }
@@ -325,7 +312,7 @@
 
     ret = mbedtls_x509_csr_parse( csr, buf, n );
 
-    mbedtls_zeroize( buf, n );
+    mbedtls_platform_zeroize( buf, n );
     mbedtls_free( buf );
 
     return( ret );
@@ -407,17 +394,17 @@
     {
         name_prv = name_cur;
         name_cur = name_cur->next;
-        mbedtls_zeroize( name_prv, sizeof( mbedtls_x509_name ) );
+        mbedtls_platform_zeroize( name_prv, sizeof( mbedtls_x509_name ) );
         mbedtls_free( name_prv );
     }
 
     if( csr->raw.p != NULL )
     {
-        mbedtls_zeroize( csr->raw.p, csr->raw.len );
+        mbedtls_platform_zeroize( csr->raw.p, csr->raw.len );
         mbedtls_free( csr->raw.p );
     }
 
-    mbedtls_zeroize( csr, sizeof( mbedtls_x509_csr ) );
+    mbedtls_platform_zeroize( csr, sizeof( mbedtls_x509_csr ) );
 }
 
 #endif /* MBEDTLS_X509_CSR_PARSE_C */