libuinput.c: sync event after a sequence

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

The program use the library libuinput to send a sequence of keyboard events.
The sequence is 'qwerty', but the demo register only the event of keys 'qwery',
so the final result will be 'qwery' because the input sistem ignores
unregistered events

Signed-off-by: Federico Vaga <federico.vaga@gmail.com>
add .gitignore to the repository

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