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/asn1parse.c b/lib/libmbedtls/mbedtls/library/asn1parse.c
index b870ca7..171c340 100644
--- a/lib/libmbedtls/mbedtls/library/asn1parse.c
+++ b/lib/libmbedtls/mbedtls/library/asn1parse.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  Generic ASN.1 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.
@@ -28,6 +28,7 @@
 #if defined(MBEDTLS_ASN1_PARSE_C)
 
 #include "mbedtls/asn1.h"
+#include "mbedtls/platform_util.h"
 
 #include <string.h>
 
@@ -43,11 +44,6 @@
 #define mbedtls_free       free
 #endif
 
-/* Implementation that should never be optimized out by the compiler */
-static void mbedtls_zeroize( void *v, size_t n ) {
-    volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
-}
-
 /*
  * ASN.1 DER decoding routines
  */
@@ -313,7 +309,7 @@
 
     if( *p == end )
     {
-        mbedtls_zeroize( params, sizeof(mbedtls_asn1_buf) );
+        mbedtls_platform_zeroize( params, sizeof(mbedtls_asn1_buf) );
         return( 0 );
     }
 
@@ -358,7 +354,7 @@
     mbedtls_free( cur->oid.p );
     mbedtls_free( cur->val.p );
 
-    mbedtls_zeroize( cur, sizeof( mbedtls_asn1_named_data ) );
+    mbedtls_platform_zeroize( cur, sizeof( mbedtls_asn1_named_data ) );
 }
 
 void mbedtls_asn1_free_named_data_list( mbedtls_asn1_named_data **head )