Remove momentum reduction in CA_JUMPTHOK

Also add new multiability handling for it
SRB2 2.1.10 release
Merge branch 'next'
Merge branch 'master' into next
Merge pull request #28 from wolfy852/master

Remove momentum reduction in CA_JUMPTHOK
SRB2 2.1.11 release
Merge branch 'next'
evil changes
SDL2: Fix 320x200 mode
SDL2: Reimplement some stubbed commands

Also remove some unnecessary functions.
SDL2: Do not use xinput, force directinput

Fixes axes issue with xinput controllers.
SDL2: Add 1600x1200 mode