chan_dahdi: Populate CALLERID(ani2) for incoming calls in featdmf signaling mode.

For the featdmf signaling mode the incoming MF Caller-ID information is
formatted as follows: *${CALLERID(ani2)}${CALLERID(ani)}#*${EXTEN}#

Rather than discarding the ani2 digits, populate the CALLERID(ani2) value
with what is received instead.

AST-1368 #close
Reported by: Denis Martinez
Patches:
      extract_ani2_for_featdmf_v11.patch (license #5621) patch uploaded by Richard Mudgett


git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/11@429783 65c4cc65-6c06-0410-ace0-fbb531ad65f3