Legacy ref_interface_t texture access is not refcountable. It does
create/destroy texture in a single call regardless of other users.
Track it with a separate flag that affects refcount with a single +1/-1.
Too many places in the engine and the renderer expect texture names to
be insensitive: RAD files, material references, probably engine and game
calls too.
Make it universally case insensitive. Also, add rudimentary tests for
it.
Ivan Avdeev