Simplify build-time config checks.

These now simply reflect whatever config.hpp reports, and are therefore always in synch with the headers.
They are also now compile-time tests only, which means they function with cross compilers.
Fixes: https://svn.boost.org/trac/boost/ticket/12805.

test/config_info.cpp

@@ -1152,6 +1152,11 @@ void print_boost_macros()
 
 
 
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    // END GENERATED BLOCK