chan_gulp: Minor readability Improvements to chan_gulp

(closes issue ASTERISK-21670)
Reported by: Snuffy
Review: https://reviewboard.asterisk.org/r/2473/
Patches:
    gulp-coding-guide.diff uploaded by snuffy (license 5024)



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@388526 65c4cc65-6c06-0410-ace0-fbb531ad65f3