Doomsday Engine

IdTech1Converter: Updated MAPINFO translation, minor compatibility fixes

When extracting a number from a string ZDoom uses atoi-like behavior.
Also added translations for various ZDoom properties which we now use
in the default MAPINFO data.

Note that achieving ZDoom-compatible MAPINFO behavior is out of scope
for the 1.15 release.

Todo: Revise music song/track attribution.