[X11] Reconcile logical keyboard state with physical state on FocusIn

since the window system doesn't do it for us like other platforms.

This prevents sticky keys and missed keys when going in and out
of focus, for example Alt would appear to stick if switching away
from an SDL app with Alt-Tab and had to be pressed again.

CR: Sam

premake/projects/testtimer.lua

@@ -0,0 +1,28 @@
+-- Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
+--
+-- This software is provided 'as-is', without any express or implied
+-- warranty.  In no event will the authors be held liable for any damages
+-- arising from the use of this software.
+--
+-- Permission is granted to anyone to use this software for any purpose,
+-- including commercial applications, and to alter it and redistribute it
+-- freely.
+--
+-- Meta-build system using premake created and maintained by
+-- Benjamin Henning <b.henning@digipen.edu>
+
+--[[
+testtimer.lua
+
+	This file defines the testtimer test project. It depends on the SDL2main
+	and SDL2 projects. It will not build on iOS.
+]]
+
+SDL_project "testtimer"
+	SDL_kind "ConsoleApp"
+	SDL_notos "ios"
+	SDL_language "C"
+	SDL_sourcedir "../test"
+	SDL_projectLocation "tests"
+	SDL_projectDependencies { "SDL2main", "SDL2" }
+	SDL_files { "/testtimer.*" }