Sending out unnecessary PROCEEDING messages breaks overlap dialing.

Sending out unnecessary PROCEEDING messages breaks overlap dialing.

Issue #16789 was a good idea.  Unfortunately, it breaks overlap dialing
through Asterisk.  There is not enough information available at this point
to know if dialing is complete.  The ast_exists_extension(),
ast_matchmore_extension(), and ast_canmatch_extension() calls are not
adequate to detect a dial through extension pattern of "_9!".

Workaround is to use the dialplan Proceeding() application early in
non-dial through extensions.

* Effectively revert issue #16789.

* Allow outgoing overlap dialing to hear dialtone and other early media.
A PROGRESS "inband-information is now available" message is now sent after
the SETUP_ACKNOWLEDGE message for non-digital calls.  An
AST_CONTROL_PROGRESS is now generated for incoming SETUP_ACKNOWLEDGE
messages for non-digital calls.

* Handling of the AST_CONTROL_CONGESTION in chan_dahdi/sig_pri was
inconsistent with the cause codes.

* Added better protection from sending out of sequence messages by
combining several flags into a single enum value representing call
progress level.

* Added diagnostic messages for deferred overlap digits handling corner
cases.

(closes issue #17085)
Reported by: shawkris

(closes issue #18509)
Reported by: wimpy
Patches:
      issue18509_early_media_v1.8_v3.patch uploaded by rmudgett (license 664)
      Expanded upon issue18509_early_media_v1.8_v3.patch to include analog
      and SS7 because of backporting requirements.
Tested by: wimpy, rmudgett

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@303765 65c4cc65-6c06-0410-ace0-fbb531ad65f3