Boost

Commit 297718b9 and GemUtil commit 12aa2c6 introduce new BOOST_SPECIAL_INCLUDE_PATH variable. It have been used sucessfully with Xfem and SplitMesh/test. But it had to be done on all CMAKE of eXlibris where it have to. It replace properly what was done in eXlibrisType. Boost version checking mechanism may have to be adapted.