Compiler: Add native relocation support to legacy containers

[seanbaxter]

Support native relocation for std::pair, std::tuple and std::array. In MIR, we should support direct place names to the subobjects. When lowering MIR to LLVM, emit calls to the accessor functions std::get to implement place subscript. This is rather critical for std::tuple which has a byzantine layout and differs between libstdc++ and libc++.