[boost] Variadic_macro_data library update

I have updated the variadic_macro_data librfary in the sandbox to version 1.2. The update does not change the functionality of the library, but adds better documentation, better-looking documentation, and updated jamfiles that allow the documentation and tests to be done in a local directory without having to move the library under a Boost distribution. See the readme.txt file in the doc sub-directory for more information. The variadic_macro_data library adds support and functionality for variadic macros to Boost as well as integrating variadic macros with the Boost PP library without changing the latter library in any way. Comments, questions, and suggestions are always welcome.