gmtime: Remove special treatment for IAR
Previous commits attempted to use `gmtime_s()` for IAR systems; however,
this attempt depends on the use of C11 extensions which lead to incompatibility
with other pieces of the library, such as the use of `memset()` which is
being deprecated in favor of `memset_s()` in C11.
diff --git a/library/threading.c b/library/threading.c
index c1834ba..9d5c4f1 100644
--- a/library/threading.c
+++ b/library/threading.c
@@ -37,7 +37,7 @@
#include "mbedtls/threading.h"
-#if !defined(_WIN32) && !defined(__IAR_SYSTEMS_ICC__) && (defined(unix) || \
+#if !defined(_WIN32) && (defined(unix) || \
defined(__unix) || defined(__unix__) || (defined(__APPLE__) && \
defined(__MACH__)))
#include <unistd.h>
@@ -51,7 +51,7 @@
*/
#define THREADING_USE_GMTIME
#endif /* !_POSIX_VERSION || 200112L > _POSIX_THREAD_SAFE_FUNCTIONS */
-#endif /* !_WIN32 && !__IAR_SYSTEMS_ICC__ && (unix || __unix || __unix__ ||
+#endif /* !_WIN32 && (unix || __unix || __unix__ ||
* (__APPLE__ && __MACH__)) */
#if defined(MBEDTLS_THREADING_PTHREAD)