Dircache: Don't expose struct dircache_entry and pointers into the cache, use IDs instead.

Only integer IDs are exposed from dircache with this. This way the cache is isolated from other modules.
This is needed for my buflib gsoc project.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@30038 a1c6a512-1295-4272-9138-f99709370657
8 files changed