json_spirit package

json_spirit builds out of the box as a cmake project. The only gotcha is that the original source site protects the download URL with a login form, so I have had mirror the original package on my website.

Also not sure what the update target is supposed to do...
> A CMake question: does specifying -DBOOST_SPIRIT_THREADSAFE enable the compiler option of the same name? Or do I need to do something a little bit different?

Is it a C preprocessor macro or CMake macro?