This makes the device ID assigning code common to all backends, by
moving it to AddDevice() instead of copy-pasting or replicating
the logic in the backends.
Also, to prepare for hotplugging, instead of relying on a name usage
count, the new ID assigning system always starts from ID 0 and tries
to assign the first ID that is not used.
Previously, the devices vector would be passed to all backends. They
would then manually push_back to it to add new devices. This was fine
but caused issues when trying to add synchronisation.
Instead, backends now call AddDevice() to fill m_devices so that it is
not accessible from the outside.
Currently only works on unix, but can be extended to other systems. Can
also be extended to do wiimotes.
Searches the Pipes folder for readable named pipes and creates a dolphin
input device out of them. Send controller inputs to the game by writing
to the file. Commands are described in Pipes.h.
Léo Lam