rename dirlink to gitlink.

Unify naming of plumbing dirlink/gitlink concept:

git ls-files -z '*.[ch]' |
xargs -0 perl -pi -e 's/dirlink/gitlink/g;' -e 's/DIRLNK/GITLINK/g;'

Signed-off-by: Junio C Hamano <junkio@cox.net>
diff --git a/list-objects.c b/list-objects.c
index 310f8d3..e5c88c2 100644
--- a/list-objects.c
+++ b/list-objects.c
@@ -87,7 +87,7 @@
 			process_tree(revs,
 				     lookup_tree(entry.sha1),
 				     p, &me, entry.path);
-		else if (S_ISDIRLNK(entry.mode))
+		else if (S_ISGITLINK(entry.mode))
 			process_gitlink(revs, entry.sha1,
 					p, &me, entry.path);
 		else