Multitouch support for the evdev input module

Hi,

I am currently experimenting with an emulated multitouch device (uinput)
on a Raspberry PI and created a patch that implements multitouch support for
SDL2 using the evdev input module.

For anyone who is interested, the patch can be found in the bug-tracker:
https://bugzilla.libsdl.org/show_bug.cgi?id=2712