Fix BETTER_BACKTRACES library detection for Fedora/RedHat/CentOS

(closes ASTERISK-17842)
Reported by: Bryon Clark
Patches:
	20110512__issue19278.diff.txt uploaded by Tilghman Lesher (license 5003)
	configure_bfd_with_dl_and_iberty.patch uploaded by Bryon Clark (license 6157)
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Merged revisions 360488 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 360489 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@360490 65c4cc65-6c06-0410-ace0-fbb531ad65f3