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/entropy_poll.c b/lib/libmbedtls/mbedtls/library/entropy_poll.c
index 4f92b51..4556f88 100644
--- a/lib/libmbedtls/mbedtls/library/entropy_poll.c
+++ b/lib/libmbedtls/mbedtls/library/entropy_poll.c
@@ -1,8 +1,8 @@
-// SPDX-License-Identifier: Apache-2.0
 /*
  *  Platform-specific and custom entropy polling functions
  *
  *  Copyright (C) 2006-2016, 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.
@@ -19,19 +19,25 @@
  *  This file is part of mbed TLS (https://tls.mbed.org)
  */
 
+#if defined(__linux__)
+/* Ensure that syscall() is available even when compiling with -std=c99 */
+#define _GNU_SOURCE
+#endif
+
 #if !defined(MBEDTLS_CONFIG_FILE)
 #include "mbedtls/config.h"
 #else
 #include MBEDTLS_CONFIG_FILE
 #endif
 
+#include <string.h>
+
 #if defined(MBEDTLS_ENTROPY_C)
 
 #include "mbedtls/entropy.h"
 #include "mbedtls/entropy_poll.h"
 
 #if defined(MBEDTLS_TIMING_C)
-#include <string.h>
 #include "mbedtls/timing.h"
 #endif
 #if defined(MBEDTLS_HAVEGE_C)
@@ -44,7 +50,8 @@
 #if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
 
 #if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
-    !defined(__APPLE__) && !defined(_WIN32)
+    !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && \
+    !defined(__HAIKU__)
 #error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
 #endif
 
@@ -92,6 +99,7 @@
 #include <sys/syscall.h>
 #if defined(SYS_getrandom)
 #define HAVE_GETRANDOM
+#include <errno.h>
 
 static int getrandom_wrapper( void *buf, size_t buflen, unsigned int flags )
 {
@@ -101,47 +109,8 @@
     memset( buf, 0, buflen );
 #endif
 #endif
-
     return( syscall( SYS_getrandom, buf, buflen, flags ) );
 }
-
-#include <sys/utsname.h>
-/* Check if version is at least 3.17.0 */
-static int check_version_3_17_plus( void )
-{
-    int minor;
-    struct utsname un;
-    const char *ver;
-
-    /* Get version information */
-    uname(&un);
-    ver = un.release;
-
-    /* Check major version; assume a single digit */
-    if( ver[0] < '3' || ver[0] > '9' || ver [1] != '.' )
-        return( -1 );
-
-    if( ver[0] - '0' > 3 )
-        return( 0 );
-
-    /* Ok, so now we know major == 3, check minor.
-     * Assume 1 or 2 digits. */
-    if( ver[2] < '0' || ver[2] > '9' )
-        return( -1 );
-
-    minor = ver[2] - '0';
-
-    if( ver[3] >= '0' && ver[3] <= '9' )
-        minor = 10 * minor + ver[3] - '0';
-    else if( ver [3] != '.' )
-        return( -1 );
-
-    if( minor < 17 )
-        return( -1 );
-
-    return( 0 );
-}
-static int has_getrandom = -1;
 #endif /* SYS_getrandom */
 #endif /* __linux__ */
 
@@ -152,22 +121,21 @@
 {
     FILE *file;
     size_t read_len;
+    int ret;
     ((void) data);
 
 #if defined(HAVE_GETRANDOM)
-    if( has_getrandom == -1 )
-        has_getrandom = ( check_version_3_17_plus() == 0 );
-
-    if( has_getrandom )
+    ret = getrandom_wrapper( output, len, 0 );
+    if( ret >= 0 )
     {
-        int ret;
-
-        if( ( ret = getrandom_wrapper( output, len, 0 ) ) < 0 )
-            return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
-
         *olen = ret;
         return( 0 );
     }
+    else if( errno != ENOSYS )
+        return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
+    /* Fall through if the system call isn't known. */
+#else
+    ((void) ret);
 #endif /* HAVE_GETRANDOM */
 
     *olen = 0;