Fix station ringback; trunk hangup issues in SLA

This patch fixes two bugs:
 * If an outbound call is made from a SLA phone using SLAStation, then there is
   no ringtone audible to the phone that originates the call. The indication of
   the ringing was not being passed to the SLA station; this patch fixes that
   by passing through the progress indications.
 * If an SLA station hangs up before the called party answers, then the channel
   to the called party continues to ring until a timeout occurs. If the called
   party manages to answer, Asterisk attempts to connect the called party to
   a non-existant MeetMe room. This patch corrects the behavior by abandoning
   the call attempt if it detects that the SLA station is no longer in use
   while attempting to call the called party.

Review: https://reviewboard.asterisk.org/r/2275/

(closes issue ASTERISK-20462)
Reported by: dkerr
patches:
  asterisk-11-bugid20440+20462.patch uploaded by dkerr (license 5558)
  asterisk-11-bugid20462.patch uploaded by dkerr (license 5558)

(closes issue ASTERISK-20440)
Reported by: dkerr
patches:
  asterisk-11-bugid20440.patch uploaded by dkerr (license 5558)
  asterisk-11-bugid20440+20462.patch uploaded by dkerr (license 5558)
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Merged revisions 379825 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 379826 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@379828 f38db490-d61c-443f-a65b-d21fe96a405b
Add ControlPlayback manager action

This patch adds the capability for asynchronous manipulation of audio being
played back to a channel though a new AMI action "ControlPlayback". The
ControlPlayback action supports a number of operations, the availability of
which depend on the application being used to send audio to the channel.
When the audio playback was initiated using the ControlPlayback application
or CONTROL STREAM FILE AGI command, the audio can be paused, stopped,
restarted, reversed, or skipped forward. When initiated by other mechanisms
(such as the Playback application), the audio can be stopped, reversed, or
skipped forward.

Review: https://reviewboard.asterisk.org/r/2265/

(closes issue ASTERISK-20882)
Reported by: mjordan



git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@379830 f38db490-d61c-443f-a65b-d21fe96a405b