Fixes several call transfer issues with chan_misdn.

Fixes several call transfer issues with chan_misdn.

*  issue #14355 - Crash if attempt to transfer a call to an application.
Masquerade the other pair of the four asterisk channels involved in the
two calls.  The held call already must be a bridged call (not an
applicaton) or it would have been rejected.

*  issue #14692 - Held calls are not automatically cleared after transfer.
Allow the core to initate disconnect of held calls to the ISDN port.  This
also fixes a similar case where the party on hold hangs up before being
transferred or taken off hold.

*  JIRA ABE-1903 - Orphaned held calls left in music-on-hold.
Do not simply block passing the hangup event on held calls to asterisk
core.

*  Fixed to allow held calls to be transferred to ringing calls.
Previously, held calls could only be transferred to connected calls.
*  Eliminated unused call states to simplify hangup code.
*  Eliminated most uses of "holded" because it is not a word.

(closes issue #14355)
(closes issue #14692)
Reported by: sodom
Patches:
      misdn_xfer_v14_r205839.patch uploaded by rmudgett (license 664)
Tested by: rmudgett

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@206487 65c4cc65-6c06-0410-ace0-fbb531ad65f3