crt/libsrc: include string.h for memcmp prototype

This fixes i686 gcc warning: no previous prototype for 'memcmp'

Signed-off-by: Biswapriyo Nath <nathbappai@gmail.com>
Signed-off-by: Liu Hao <lh_mouse@126.com>

mingw-w64-crt/libsrc/memcmp.c

diff --git a/mingw-w64-crt/libsrc/memcmp.c b/mingw-w64-crt/libsrc/memcmp.c
index 11f5f9c..8f11f5c 100644
--- a/mingw-w64-crt/libsrc/memcmp.c
+++ b/mingw-w64-crt/libsrc/memcmp.c
@@ -6,6 +6,7 @@
 
 #define __CRT__NO_INLINE
 #include <stddef.h>
+#include <string.h> /* for memcmp prototype */
 
 int __cdecl memcmp(const void *_S1, const void *_S2, size_t _N)
 {