The rdpContext gets an event which will
get set if an error occoured in a channel.
If a thread or a void callback has to report an
error it will get signaled by this system.
With BOOL as return type it is not possible to differentiate between
success and "no data can be read" (when a channel read would block).
rdpsnd_server_handle_messages returns now int with the following
possible values:
-1 if no data could be read
0 error (like connection close) (formerly FALSE)
1 succsess (also if further bytes need to be read) (formerly TRUE)
Not using -1 for error cases was chosen to be compatible with the BOOL
return values used before.
MS-RDPEA 2.2.2.3 states (Appendix A <6>) that quality mode PDU
should be ignored if the client version is < 6. For these clients the sound
channel got never activated since activated was only called after
reception of the quality mode PDU.
For clients < version 6 activated is now called after
CLIENT_AUDIO_VERSION_AND_FORMATS was received.
