WinGDI center window properly

Takes taskbars ant the like into consideration
Option to hide cursor for WinGDI (too)

And some cleanup
WinGDI: Lower cpu usage to ~0%

This should not have any performance hit on the gamespeed.
WinGDI: Revive dead character(s)

so we dont have to double-tap '^' on localized keyboards
Merge batch of windows-specific fixes blindly because we don't have any windows devs.

Conflicts:
	wincurse.cpp