Handling C++11

[Marcus Calhoun-Lopez]

> The *only* time you should use a libstdc++ different from the system-provided one (or ones, on 10.7) is the current LibcxxOnOlderSystems --- which explicitly loses compatibility with all Apple-provided C++ libraries
Please forgive my ignorance, but doesn’t setting _GLIBCXX_USE_CXX11_ABI=0 make
the 4.2 libstdc++ from the system and the 5.1 libstdc++ from MacPorts ABI compatible
(https://gcc.gnu.org/onlinedocs/gcc-5.2.0/libstdc++/manual/manual/using_dual_abi.html)?

> gcc 5.1 libstdc++ is GPL3 and poses significant license issues with respect to distributing binaries, among others.
Again, there may be something important I am missing, but isn’t there a GCC runtime library exceptions that ameliorates this concern
(https://gcc.gnu.org/onlinedocs/libstdc++/manual/license.html)?

Thanks,
Marcus