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>

commit.c

@@ -102,7 +102,7 @@ static unsigned long parse_commit_date(const char *buf)
 static struct commit_graft {
 	unsigned char sha1[20];
 	int nr_parent;
-	unsigned char parent[][20]; /* more */
+	unsigned char parent[0][20]; /* more */
 } **commit_graft;
 static int commit_graft_alloc, commit_graft_nr;