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.
Add support for HiDPI modes

When HiDPI is enabled, the size of the OpenGL surface (specified in
pixels) may no longer correspond to the size of the window (specified
in points). Width, Height, ClientSize and ClientRectangle return the
size of the OpenGL surface in device-dependent pixel coordinates
(origin: top-left pixel of the surface). Bounds and Size return the
size of the window in device-independent point coordinates (origin:
desktop).
Initial implementation of IJoystickDriver API
New SDL2 library with HiDPI support

Upgraded SDL2 to hg 7778:a571a9947869, which includes support for the
new SDL_WINDOW_HINT_HIDPI flag.
Display joystick information
Sdl2JoystickDriver.Poll() and axis fixes
No separate Factory.Embedded for SDL2

Sdl2Factory supports both desktop and embedded profiles, there is no
need to construct a separate Embedded profile.
Implemented IDisposable in Sdl2Joystick

Sdl2Joystick calls SDL_JoystickOpen, which means we must call
SDL_JoystickClose on shutdown.
Moved all input processing to Sdl2InputDriver

This reduces the duplication of code between Sdl2NativeWindow and
Sdl2InputDriver. Sdl2InputDriver is now solely responsible for handling
input.
Fixed file not found error

The debug.log would be deleted after launching an example, causing the
example browser to complain that the file cannot be found. In reality,
it should be deleted before launching an example - fixed.
Fixed git revision detection
Use 7z wildcards to zip tree

Using msbuild/xbuild wildcards results in different behavior between the two implementations. Since we require 7z anyway, it is simpler if we just use that directly.
Do not copy Dependencies

Since the Example Browser is not loading its Dependencies by itself, there is no point in copying them to the output directory.
HIDPI support requires SDL > 2.0.0

SDL_GL_GetDrawableSize was introduced after 2.0.0, so we need to check for that version before we call this method. Fixes MethodNotFounException on vanilla libsdl2-2.0.0 on linux.
Fixed line endings
Always Set HIDPI flag

It does not to set this flag on previous SDL2 versions, it is ignored silently when not supported.
Merge branch 'scancodes'

Conflicts:
	Source/OpenTK/OpenTK.csproj
	Source/OpenTK/Platform/Windows/WinFactory.cs
Added line-ending conversions