Remove an old workaround that was kept around for ABI-compatibility on x86-64 between different LLVM versions. This means LLVM r67588 is required if you want to compile for x86-64, otherwise the backend will assert when you try to return e.g. struct { int i; char c; } from a function. (In particular, this is no longer compatible with LLVM 2.5) It also means that any code returning small structs on x86-64 will probably need to be recompiled in order to be linkable to code compiled with this change.

void main()
{
    int* e = __errno_location();
    printf("&errno = %p\n", e);
    printf("errno = %d\n", *e);
}

extern(C):
version(darwin) {
    int* __error();
    alias __error __errno_location;
} else {
    int* __errno_location();
}
int printf(char*,...);