Fix segfault in mod_cdr_mongo when "number" is null. Thanks Dave May for bug report and patch. Fixes FS-4843.

make it so when you put someone on hold and then they attended transfer you, the resulting bridge will still be playing hold music

Add att_xfer_destination_number variable to indicate the original destination number of the attended transfer leg on REFER for semi-attended transfer scenarios.

Differentiate when the sms message successfully matched an extension in the chatplan, and when it fell through.

Fire an event on successful sms delivery, as well as clearify if the delivery method was blocking or not.

get an EOP, we no longer worry whether the final stages tidy up. This helps
tolerate the increasing number of VoIP calls which hang up before the audio has
flushed down the line.

A few little cleanups.

Use peerhangup flag variable to track whether a hangup has been
initiated by the peer or libpri itself (e.g. Layer 2 timeouts).

These changes fix a couple of problems with hangup events not being
handled properly in some situations:

  - Call abort caused by incoming RESTART on a channel in use
  - T309 timeout after L2 loss
  - Improved hangup handling in libpri-side on_hangup() event handler
    and state_advance() (FreeTDM side)
Signed-off-by: Stefan Knoblich <stkn@openisdn.net>