This commits lays the foundation for actions in Monado (input and output).
There are lots of things missing and non-conformant in there. But once in
more people then just me can test it out and work on it.
This patch has been spun of the rather massive amount of work for adding input
devices into Monado. The interfaces feels somewhat stable now so could do
with another pair of eyes on them, before too much work is done on st/oxr.