Fixed issue #44.

Removed unnesessary include <sys/types.h> from stdio.h, stdlib.h,
string.h, strings.h and time.h.

include/string.h

@@ -3,12 +3,15 @@
  * All rights reserved.  The Berkeley software License Agreement
  * specifies the terms and conditions for redistribution.
  */
-#include <sys/types.h>
-
 #ifndef	NULL
 #define	NULL	0
 #endif
 
+#ifndef _SIZE_T
+#define _SIZE_T
+typedef unsigned size_t;
+#endif
+
 char	*strcat (char *, const char *);
 char	*strncat (char *, const char *, size_t);
 char	*strcpy (char *, const char *);