When the Intellisense compiler is being used wihin the Visual Studio IDE, both __EDG__ and __INTELLISENSE__ are defined along with the usual VC++ predefines. This change adjusts the Boost PP configuration to take into account that situation.

When using clang variadic macro support is now dependent on the C or C++ version system, and not automatically turned on in all situations. This reduces clang warnings.

Create metadata file.

Changed BOOST_PP_EMPTY to only use the variadic version when not VC++. Corrected others to use local version of EMPTY.