Add raop version defines
Pass timestamp from raop_buffer to caller
Add byte helpers to read write big endinan values
Switch to generic bio routines in some places
Pass timestamps up in process step to client
Add ntp sync code and conversion function from timestamp to system clock
Add wrapper to get clock which adds NTP base clock

This let implementor set clock as relative to system start,
which is what normal itunes uses.
Signal sync packet to library user
Bump minor for API breakage