Recapitulation of milestone 3: * Ported GCC and Clang std::vector. * Implemented the rest of std::string for MSVC, GCC, and Clang. * Fixed issue 20235[1] which was a blocker for both std::string and std::vector. * Fixed a mangling issues which was blocking std::pair. [1] : https://issues.dlang.org/show_bug.cgi?id=20235