Stop startpage from opening itself as an archive

For real this time. This is done by making sure the paths to the archive
to be opened and the path to the startpage are in the same format.
Fixed typo in ZDoom languages.
Added stripped-down ZDoom MIDI conversion setup

This finally allows to play back HMI, HMP, and XMI songs.
Removed unused baggage from new MIDI readers
Removed more needless baggage.
Added TGA, TIFF, and PCX to potential patches.

It's supported by ZDoom and TGA patches are used in the Wolf3D TC.