remove C11 requirement and add stdc macro support

Author: bassiounix

libc/include/llvm-libc-macros/annex-k-macros.h

@@ -9,8 +9,9 @@
 #ifndef LLVM_LIBC_INCLUDE_LLVM_LIBC_MACROS_ANNEX_K_MACROS_H
 #define LLVM_LIBC_INCLUDE_LLVM_LIBC_MACROS_ANNEX_K_MACROS_H
 
-#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L &&                \
-    defined(__STDC_WANT_LIB_EXT1__) && __STDC_WANT_LIB_EXT1__ == 1
+#define __STDC_LIB_EXT1__ 200509L
+
+#if defined(__STDC_WANT_LIB_EXT1__) && __STDC_WANT_LIB_EXT1__ == 1
 
 #define LIBC_HAS_ANNEX_K