Hide player name input fields for not-configured players.
Remove unused headers from project.
Fix ambiguous comment.
Fix pascal/C syntax discrepancy.
Remove useless return variable from Draw()/DrawFG()/DrawBG() methods.
Fix ALT modifier check.
Warning fixes.
Implement support for mousewheel scrolling of select sliders.
Originally I implemented generic support for left/right behaviour but this would have
caused conflicting behaviour, so for now just implement the scroll behaviour specifically
for slider controls.