Revert "Replace zero-length array decls with []."

This reverts 6c5f9baa3b commit, whose
change breaks gcc-2.95.

Not that I ignore portability to compilers that are properly C99, but
keeping compilation with GCC working is more important, at least for
now.  We would probably end up declaring with "name[1]" and teach the
allocator to subtract one if we really aimed for portability, but that
is left for later rounds.

Signed-off-by: Junio C Hamano <junkio@cox.net>

receive-pack.c

@@ -24,7 +24,7 @@ struct command {
 	unsigned char updated;
 	unsigned char old_sha1[20];
 	unsigned char new_sha1[20];
-	char ref_name[];
+	char ref_name[0];
 };
 
 static struct command *commands = NULL;