Experimental: Don't reverse parameter order for extern(D) on x86_64.

[kinke]

Requires ldc-developers/druntime#19 and ldc-developers/phobos#9.
Debug unittests pass on Linux x64 with LLVM 3.5, but dmd-testsuite reveals a serious bug:

import core.stdc.stdio;
import std.algorithm;

struct Shell
{
    string str;

    const int opCmp(ref const Shell s)
    {
    return std.algorithm.cmp(this.str, s.str);
    }
}

void main()
{
    Shell[3] a;

    a[0].str = "hello";
    a[1].str = "betty";
    a[2].str = "fred";

    a.sort;

    foreach (Shell s; a)
    {
    printf("%.*s\n", s.str.length, s.str.ptr);
    }

    assert(a[0].str == "betty");
    assert(a[1].str == "fred");
    assert(a[2].str == "hello");
}

a.sort() sorts the array in reversed order.

[kinke]

I've just updated the druntime patch - I've previously missed TypeInfo_Struct.compare() which reverses the arguments when invoking _xopCmp(). The test case above now works.

[kinke]

It finally seems to be working now (except for the 32-bit tests). The front-end hack is ugly and can't be incorporated as-is, but I guess the proper location to fix it is the upstream front-end.

[kinke]

Upstream PR: dlang/dmd#5232

[kinke]

Closing because this has finally been implemented in v1.29.