Fixed DStress tests nocompile/c/{const_32_B.d,const_32_C.d}. Updated the runtest script to build libtangobos-partial.a if it hasn't already been built. Added in signbit() and va_arg!()() to libtangobos-partial.a so more of the phobos dependent DStress tests pass.

module nested2;

void func(ref int i)
{
    delegate {
        assert(i == 3);
        i++;
    }();
}

void main()
{
    int i = 3;
    func(i);
    assert(i == 4);
}