* implement M_getenv for compatibility with non-Latin paths on Windows
* use regular wcslen
SDL_wcslen is undocumented
* fix memory leak
* cache the `wenv == NULL` case
* add libtextscreen
* add doomkeys.h
* fix format string warnings
* delete all files unnecessary for ENDOOM
* add ENDOOM support
* show ENDOOM screen in the same window as the game
* add PWADs only option, add comments
* change PWADs->PWAD