Allow mISDN to send PROGRESS messsage.

* Made isdn_msg_parser.c build a progress message with the mandatory
progress indicator IE.  (The mISDNuser NT state machine rejected sending
the incomplete message.)

Note: The associated mISDN and mISDNuser patches respectively are viewable
here:
http://svnview.digium.com/svn/thirdparty?view=rev&rev=200
http://svnview.digium.com/svn/thirdparty?view=rev&rev=201

(closes issue AST-1153)
Reported by: Guenther Kelleter
Patches:
      progress-chan_misdn.diff (license #6372) patch uploaded by Guenther Kelleter
      progress-misdn.diff (license #6372) mISDN patch uploaded by Guenther Kelleter
      progress-misdnuser.diff (license #6372) mISDNuser patch uploaded by Guenther Kelleter
........

Merged revisions 388425 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 388426 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@388427 f38db490-d61c-443f-a65b-d21fe96a405b