Cosa è cambiato in EDuke32, build per build

- make PGUP/PGDN and HOME/END behave as expected across all menus - in keyboard/mouse button mapping menu, draw function names that have been given custom names via CON with pal 8 for easier recognition - fix tinting of function names in mouse button mapping menu

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.