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: http://svn.asterisk.org/svn/asterisk/trunk@388526 f38db490-d61c-443f-a65b-d21fe96a405b