Removed support for < Windows XP

The support burden for Windows versions prior to XP was too large, plus
the relevant code was completely untested. Removing that will allow us
to focus on the things that really matter.
Added common key aliases
Use locale-independent scancodes

This significantly improves the usability of keyboard input, by allowing
a common input scheme to be used on different keyboard layouts. Text
input will be facilitated through a new API.
Merge branch 'scancodes'

Conflicts:
	Source/OpenTK/OpenTK.csproj
	Source/OpenTK/Platform/Windows/WinFactory.cs