Add check of compiler's C++ Standard Library

Use try_run to compile and run a simple C++ program that outputs the
Standard C++ Library in use at compile/link time. Support GNU and
libc++ libraries only for now. Currently this try_run will not
work when cross-compiling.

See also the Boost.Predef library, which could possibly be used either
by find_package, or as an import using bcp

http://www.boost.org/doc/libs/1_55_0/libs/predef/doc/html/index.html