Add a check for <unistd.h> providing a prototype for getopt() which is compatible

with the one in	include/getopt.h.  If so then define HAVE_DECL_GETOPT.

binutils/config.in

@@ -178,6 +178,9 @@
 /* Is the type time_t defined in <sys/types.h>? */
 #undef HAVE_TIME_T_IN_TYPES_H
 
+/* Is the prototype for getopt in <unistd.h> in the expected format?  */
+#undef HAVE_DECL_GETOPT
+
 /* Does <utime.h> define struct utimbuf? */
 #undef HAVE_GOOD_UTIME_H