cmake:
* new option SDL2_API
* drop GLSL_SHADER_DIR. Useless, shaders are embedded in .h file
* use some hardening flags (for the moment only basic one)
onepad:
* port the code to SDL2 (Note only SDL1 is supported for the moment)
* improve detection of button vs axis (long-standing issue)
* avoid potential overflow on mouse mouvement detection


git-svn-id: http://pcsx2.googlecode.com/svn/trunk@5756 96395faa-99c1-11dd-bbfe-3dabce05a288