This lets us get rid of the Reset call in ProcessInputPayload, which was
causing us some threading headaches (see 74ed5e5532). Instead we handle
disconnection in the same way as the libusb implementation does.
We can register a BroadcastReceiver to have Android tell us when a GC
adapter gets connected instead of having a loop where we continuously
call SleepCurrentThread(1000) and poll the current status. When waiting
for a GC adapter to connect, this both reduces power usage and improves
responsiveness.
Note that I made openAdapter get the UsbDevice that's been stored by the
hotplug code instead of having openAdapter find the UsbDevice on its own
like before. This is only because I want to ensure that the UsbDevice
being tracked for disconnection is the same as the UsbDevice actually
being used, in case the user has multiple adapters connected.
The read thread could call Reset, which in turn tried to join the read
thread, leading to a SIGABRT. This manifested as Dolphin consistently
crashing when disconnecting a GC adapter and having a chance of crashing
a few seconds after connecting a GC adapter.
