This tries to reduce the number of IdeFile we will create by caching
them. When creating a new file with new funcs (some code will need to be
ported to use this), we lock the cache and try to return a previous entry.

Another thing I'd like to cleanup (well other than possibly removing
IdeFile altogether), is to drop the file-settings after some period of
innactivity. We might event to only support loading them, and not keep
a copy for future use.