shared: make cgit_free_taginfo() public

We will use this function from ui-tag.c in the next patch.

Signed-off-by: John Keeping <john@keeping.me.uk>
diff --git a/cgit.h b/cgit.h
index 7df0e3a..df42312 100644
--- a/cgit.h
+++ b/cgit.h
@@ -344,6 +344,7 @@
 			int flags, void *cb_data);
 
 extern void cgit_free_commitinfo(struct commitinfo *info);
+extern void cgit_free_taginfo(struct taginfo *info);
 
 void cgit_diff_tree_cb(struct diff_queue_struct *q,
 		       struct diff_options *options, void *data);