Do we have to define ```BigEndian/LittleEndian``` and ```D_LP64``` here as well, or are ```TARGET_BIG_END``` and ```TARGET_64BIT``` always defined so that we can add that code directly to ```d-lang.cc```?

BTW: I've started to add those macros following the CPP macro defintions: https://gist.github.com/4586733 There's of course still a lot to do.