(CMAKE ROSE) new Boost CMake option

This commit introduces the Boost_USE_MULTITHREADED option.
By default this is OFF.  This means that ROSE will link against
the non-multithreaded versions of the Boost libraries.
If a developer wishes to build ROSE using Boost's multithreaded
libraries, they can turn Boost_USE_MULTITHREADED ON.
Merge commit 'cbc482c088f794d52fb31267d1b280cb0e7901c8' into HEAD