GameSettingsScreen: Disable a bunch of options when software rendering is enabled.
They don't do anything when software rendering is enabled, so there's bound to be confusion caused by these options continuing to be enabled.

Conflicts:
	UI/GameSettingsScreen.cpp
Disable more stuff, and use cached booleans instead.

Conflicts:
	UI/GameSettingsScreen.cpp
Do it for post-processing and resolution too, to be consistent.
Throw "Disable Alpha Test" into the pile of options to be disabled.
Buildfix.
Merge pull request #6285 from thedax/disable-ui-options

GameSettingsScreen: Disable a bunch of options when software rendering is enabled.