(cherry picked from commit 8fe74bf0f90aab0b23d5ff21079cba4201bb4fdf)
(cherry picked from commit 92cd9bd70db460fdce4af0596cf9d8ee3c3abad5)
(cherry picked from commit cc6dec72863a771da0c0f3ab3d32f75d7ce863bd)
Note: This adds support for using jemalloc on FreeBSD, Mac OS X Lion and a few other platforms (not enabled by default) Please read dep/jemalloc/ChangeLog for further information (Changed from 2.1.1 and up apply)