libuinput.h: add library's API

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
libuinput.c: add library's core

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
Makefile: to compile the library

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
add README

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>