BasePacketReader is badly-behaved if read_packet is not continually drained

[Ralith]

Pushing every page of a complete ogg file before attempting to read any packets will result in lost packets.

[est31]

Yeah there is only limited buffering. Maybe this should be pointed out.

[Ralith]

It is very convenient when coupling push-based and pull-based interfaces to push all your data before trying to drain packets, so having undocumented breakage there is definitely an unpleasant surprise.