Remove g_pWindowHandle.

Now that the EmuWindow is gone we don't need the global anymore. The Host should provide a window handle for the renderer.
Update documentation.
Don't create a Panel for a seperate render window.

Instead of setting RenderParent to null and raising complexity RenderFrame can be its own parent.
Remove CPanel.

Let the RenderFrame handle those messages.
Remove wxTAB_TRAVERSAL style from RenderFrame.
Fix RendererHasFocus().
Prevent DXGI from making changes to the window.

Prevents DXGI from responding to Alt+Enter and messing up our fullscreen handling.
D3D: Request desktop resolution before overriding the buffer size.

This fixes issues where the wrong refresh rate is selected for some monitors.
D3D: Add exclusive fullscreen support.
Exit fullscreen when user is prompted to confirm stop.

And fix a small typo while we're are it.