[X11] Added dllmap for Mac OS X (XQuartz)
[X11] Match win32 wheel coordinate system

OpenTK uses the win32 wheel coordinate system, where
(+h, +v) = (right, up). XI2 uses (+h, +v) = (right, down)
instead, so we need to flip the vertical offset.

Fixes issue #133 and https://github.com/mono/MonoGame/issues/2686
[Mac] Match win32 scrolling coordinates
[Mac] Add note for higher precision pixel scroll
[Mac] Fix Mouse.GetState() h-wheel

External mice will now report horizontal scrolling in the low-level
`Mouse.GetState()` API. The touchpad apparently creates an emulated
mouse device that does not report horizontal wheel scrolling events.

Touchpad support probably requires a proper multitouch implementation.
Merge pull request #134 from thefiddler/scrollfix

[Mac][X11] Match win32 wheel coordinate system
Merge branch 'xquartz' of https://github.com/thefiddler/opentk into xquartz
[X11] Implement support for XQuartz (X11 on Mac)
[X11] Check before monitoring /dev/input

This avoids a crash on non-Linux systems that do not support /dev/input.
[X11] Throw exception if GLX is not supported

You cannot create an X11/OpenGL context without the GLX extension.
OpenTK will now throw a `NotSupportedException` when this condition is
encountered.

In some cases, it may be possible to enable the EGL backend by passing
`GraphicsContextFlags.Embedded` to the `GraphicsContext` constructor.
[X11] Added glXQueryVersion DllImport.
[X11] Construct X11 Factory first if enabled

This allows us to use X11 on Windows and Mac, if explicitly requested
by the user via `ToolkitOptions.Backend`.
[X11] Remove unused XCreateWindow overloads
[X11] Send ClientMessage to exit input event loop

To do that, we need a custom InputOnly window. This window is only used
for receiving the exit ClientMessage - XI2 input is still received
through the root window.

Fixes issue https://github.com/mono/MonoGame/issues/2711
Merge pull request #135 from thefiddler/xquartz

XQuartz support (X11 on Mac)
Merge pull request #138 from thefiddler/xi2exitfix

[X11] Fix hang when exiting XI2 input thread
[Convert] Workaround for broken names with spaces
[ES][GL] Synced with June 2014 specifications

This introduces support for the following extensions:
- EXT_geometry_point_size
- EXT_primitive_bounding_box
- EXT_texture_array
- EXT_tessellation_point_size
[ES][GL] Regenerated bindings
Fixes bugs in String marshalling.

Fixes two issues:
1. FreeStringArrayPtr used the wrong variable in the offset to
ReadIntPtr causing an access violation.
2. Better cleanup of memory in MarshalStringArrayToPtr when any alloc
fails.