dir.h: refactor to no longer need to include cache.h

Moving a few functions around allows us to make dir.h no longer need to
include cache.h.  This commit is best viewed with:
    git log -1 -p --color-moved

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pathspec.h

@@ -171,6 +171,11 @@ int match_pathspec_attrs(struct index_state *istate,
 			 const char *name, int namelen,
 			 const struct pathspec_item *item);
 
+int match_pathspec(struct index_state *istate,
+		   const struct pathspec *pathspec,
+		   const char *name, int namelen,
+		   int prefix, char *seen, int is_dir);
+
 /*
  * Determine whether a pathspec will match only entire index entries (non-sparse
  * files and/or entire sparse directories). If the pathspec has the potential to