DAHDI ISDN channel names will not allow device state to work. (Interim solution.)

DAHDI ISDN channel names will not allow device state to work.  (Interim solution.)

Since ISDN works like SIP and not analog ports in regard to devices, the
device state based on the ISDN channel number could not work.  This has
not been an issue until the advent of PTMP NT mode.  Previously, ISDN
lines were used as trunks and did not have to keep track of specific
devices.

As an interim solution until device states are properly implemented, the
channel name is being changed to the following format to use the generic
device state support:
DAHDI/i<span>/<number>[:<subaddress>]-<sequence-number>

Dialplan hints would thus be:
exten => xxx,hint,DAHDI/i2/5551212

This will work with the following restrictions:
*  The number of devices/phones cannot exceed the number of B channels.
(i.e., BRI has 2)
*  Each device/phone can only have one number.  No shared MSN's.
*  The phones/devices probably should not use subaddressing.

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@226882 65c4cc65-6c06-0410-ace0-fbb531ad65f3