Cosa è cambiato in EDuke32, build per build

Internally, there's a new function fade_screen_black() that implements the fading more efficiently than calling rotatesprite for classic, and uses tile 0 (assumed to have at least 64x32 size) in the GL modes. The black background of the user map selector is still done with rotatesprite and tile BLANK in every renderer.

Mapster32: Helper feature -- pressing SHIFT on a 2-sided wall makes the PGUP/PGDN etc. commands operate on the sector at the other end of the wall; replaced searchstat numbers by #defined names and eliminated the worst cases of code duplication in astub.c