The FREE_LIST_*_MT stuff was introduced on the SVN trunk in r28722
(2013-07-04), but so far, has not been merged into the v1.7 branch yet
(2013-09-06). So put it in its own #ifdef, rather than defining it
based on OMPI_MAJOR_VERSION/OMPI_MINOR_VERSION.
This commit was SVN r29148.
The following SVN revision numbers were found above:
r28722 --> open-mpi/ompi@c9e5ab9ed1