Cleanup transmit_* functions

Bulk lot of generally trivial changes for cleaning up the transmit stuff. Line state request has been modified for line only responses.

(closes issue #16994)
Reported by: wedhorn
Patches: 
      skinny-clean07.diff uploaded by wedhorn (license 30)
Tested by: wedhorn


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@255850 65c4cc65-6c06-0410-ace0-fbb531ad65f3