Implement call parking in chan_skinny.

(closes issue #11342)
Reported by: DEA
Patches:
      chan_skinny-park.txt uploaded by DEA (license 3)
      chan_skinny-park-v2.diff.txt uploaded by mvanbaak (license 7)
Tested by: DEA, mvanbaak


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@122493 65c4cc65-6c06-0410-ace0-fbb531ad65f3