Make sure memcpy() gets properly declared by including string.h.

crypto/o_time.c

diff --git a/crypto/o_time.c b/crypto/o_time.c
index 7389820..86b78e3 100644
--- a/crypto/o_time.c
+++ b/crypto/o_time.c
@@ -57,6 +57,7 @@
  */
 
 #include <openssl/e_os2.h>
+#include <string.h>
 #include "o_time.h"
 
 #ifdef OPENSSL_SYS_VMS