We try to keep the system running even when all available memory is
spent.

Review: https://reviewboard.asterisk.org/r/2734/
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Merged revisions 396279 from http://svn.asterisk.org/svn/asterisk/branches/1.8
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Merged revisions 396287 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@396309 65c4cc65-6c06-0410-ace0-fbb531ad65f3