Fix parsing of SIP headers where compact and non-compact headers are mixed

Fix parsing of SIP headers where compact and non-compact headers are mixed

Change parsing of SIP headers so that compactness of the header no longer
influences which header will be chosen.  Previously, a non-compact header
would be chosen instead of a preceeding compact-form header.

(closes issue ASTERISK-17192)
Review: https://reviewboard.asterisk.org/r/1728/
........

Merged revisions 354702 from http://svn.asterisk.org/svn/asterisk/branches/1.8

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/10@354703 65c4cc65-6c06-0410-ace0-fbb531ad65f3