Allow semicolons and extended characters in user-specified SIP headers.

(closes issue #14110)
 Reported by: gork
 Patches: 
       20081222__bug14110__2.diff.txt uploaded by Corydon76 (license 14)
 Tested by: gork, putnopvut


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@166696 65c4cc65-6c06-0410-ace0-fbb531ad65f3