Patch from Alexander Kuznetsov: Real-time File Selection, thanks for the contribution.
Still made a few minor changes from latest patch:
1. Rename SELECTEDFILE to HILITED_FILE, since we are not actually selecting the file, but previewing/highliting the possible selection.
2. Also made this clearer by not drawing the files as selected, but just highlight them.
3. Removed the Select/Deselect toggle when clicking on file, will be committed separately soon.