Added vars to d_clisrv, renamed autoexec.cfg, added menu variables to d_netcmd.h, added powers to dehacked.c for LUA, and made sure things can actually compile correctly as-is (squished two errors).

Also made fades use core functions if they are available.

MOUSE6-8 will not be supported on SDL2 as there is no interface for them.

ONLY US KEYBOARDS SUPPORTED! THAT'S HOW WE DO IT IN AMURRICA

In some cases, the warp back to center was being detected as a mouse motion, causing all sorts of silliness with the mouse. The workaround is by only using the first motion event and ignoring every event after that, until the next call to I_GetEvent.

Fixes https://mb.srb2.org/showthread.php?t=39921 where the issue before was that when you transformed your momentum would still have you moving slowly, which could cancel out the animation.