Fix cfloat return on x86_64: only perform ABI transformation for non-extern(D) functions. There's no need to waste cycles with extern(D), which we get to define ourselves. Fixes tests/mini/asm8.d. (Since the asm abiret code already assumed {xmm0, xmm1} returns)

module multiarr4;
extern(C) int printf(char*, ...);

void main()
{
    char[][] a;
    a.length = 2;
    a[0] = "hello";
    a[1] = "world";
    foreach(v;a)
    {
        printf("%.*s\n", v.length, v.ptr);
    }
}