Remove possible segfaults from res_odbc by adding locks around usage of odbc handle

(closes issue ASTERISK-19011)
Reported by: Walter Doekes
Patches:
	issueA19011_combine_read_and_write_locks_WORK_IN_PROGRESS.patch uploaded by Walter Doekes (license 5674)
review: https://reviewboard.asterisk.org/r/1719/
review: https://reviewboard.asterisk.org/r/1622/
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Merged revisions 356917 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 356961 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@356962 65c4cc65-6c06-0410-ace0-fbb531ad65f3