chan_sip: Don't ignore expires value in contact header if it lacks semicolon

chan_sip: Don't ignore expires value in contact header if it lacks semicolon

(closes issue ASTERISK-22574)
Reported by: Filip Jenicek
Patches:
    chan_sip_expires.patch uploaded by Filip Jenicek (license 6277)
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Merged revisions 400469 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 400470 from http://svn.asterisk.org/svn/asterisk/branches/11
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Merged revisions 400471 from http://svn.asterisk.org/svn/asterisk/branches/12

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@400482 65c4cc65-6c06-0410-ace0-fbb531ad65f3