Fix #6292.  mincore is broken on centos 5.8, so workaround it. {{{svn merge -r54513:54514 https://svn.tokutek.com/tokudb/toku/tokudb.6292}}}.

git-svn-id: file:///svn/toku/tokudb@54515 c7de825b-a66e-492c-adef-691d508d4ae1