Add event read dummy callback
Add event read dummy callback

It seems, that due to alsa-lib bug (or incorrect API usage within MPD
code) the read_event callback is required. Also, poll file descriptor
has to be set, otherwise poll_descriptors callback is called - which
seems like an alsa-lib bug as well.

Event notifications will be implemented anyway... someday.

Fixes #19

Arkq/bluez-alsa,guillaumezin/bluez-alsa,Arkq/bluez-alsa,Arkq/bluez-alsa,guillaumezin/bluez-alsa