Import mbedtls-2.27.0

Imports Mbed TLS 2.27.0 from https://github.com/ARMmbed/mbedtls.git
commit f71e28780841 ("Merge pull request #843 from
paul-elliott-arm/mbedtls-2.27.0rc0-pr") (tag mbedtls-2.27.0, v2.27.0).

Files that are not needed are removed.

 cd lib/libmbedtls
 rm -rf mbedtls
 cp -R path/to/mbedtls-2.27.0/mbedtls .
 cd mbedtls
 rm CMakeLists.txt DartConfiguration.tcl Makefile
 rm .gitignore .travis.yml .pylintrc .globalrc .mypy.ini BRANCHES.md
 rm include/.gitignore include/CMakeLists.txt library/.gitignore
 rm library/CMakeLists.txt library/Makefile
 rm -rf .git .github doxygen configs programs scripts tests visualc yotta
 rm -rf 3rdparty ChangeLog.d docs
 rm -rf include/mbedtls/config_psa.h include/psa
 rm library/psa_* library/mps_*
 cd ..
 git add mbedtls

This is a complete overwrite of previous code so earlier changes in the
previous branch import/mbedtls-2.22.0 will be added on top of this commit.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
diff --git a/lib/libmbedtls/mbedtls/library/gcm.c b/lib/libmbedtls/mbedtls/library/gcm.c
index ddd2d4e..f237bab 100644
--- a/lib/libmbedtls/mbedtls/library/gcm.c
+++ b/lib/libmbedtls/mbedtls/library/gcm.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  NIST SP800-38D compliant GCM implementation
  *
- *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  Copyright The Mbed TLS Contributors
+ *  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.
@@ -15,8 +15,6 @@
  *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  *  See the License for the specific language governing permissions and
  *  limitations under the License.
- *
- *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 
 /*
@@ -29,11 +27,7 @@
  * [MGV] 4.1, pp. 12-13, to enhance speed without using too much memory.
  */
 
-#if !defined(MBEDTLS_CONFIG_FILE)
-#include "mbedtls/config.h"
-#else
-#include MBEDTLS_CONFIG_FILE
-#endif
+#include "common.h"
 
 #if defined(MBEDTLS_GCM_C)
 
@@ -825,6 +819,15 @@
                                 add_len_test_data[i],
                                 pt_test_data[pt_index_test_data[i]],
                                 buf, 16, tag_buf );
+#if defined(MBEDTLS_GCM_ALT)
+            /* Allow alternative implementations to only support 12-byte nonces. */
+            if( ret == MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED &&
+                iv_len_test_data[i] != 12 )
+            {
+                mbedtls_printf( "skipped\n" );
+                break;
+            }
+#endif /* defined(MBEDTLS_GCM_ALT) */
             if( ret != 0 )
                 goto exit;