dir.c: make excluded() file scope static

Now there no longer is external callers of this interface, so we can
make it static.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

dir.c

@@ -560,7 +560,7 @@ int excluded_from_list(const char *pathname,
 	return -1; /* undecided */
 }
 
-int excluded(struct dir_struct *dir, const char *pathname, int *dtype_p)
+static int excluded(struct dir_struct *dir, const char *pathname, int *dtype_p)
 {
 	int pathlen = strlen(pathname);
 	int st;

dir.h

@@ -78,7 +78,6 @@ extern int read_directory(struct dir_struct *, const char *path, int len, const
 
 extern int excluded_from_list(const char *pathname, int pathlen, const char *basename,
 			      int *dtype, struct exclude_list *el);
-extern int excluded(struct dir_struct *, const char *, int *);
 struct dir_entry *dir_add_ignored(struct dir_struct *dir, const char *pathname, int len);
 
 /*