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 tangotests.mem5;

class SC
{
    int* ip;
    this()
    {
        ip = new int;
    }
    ~this()
    {
        delete ip;
    }
    void check()
    {
        assert(ip !is null);
    }
}

void main()
{
    scope sc = new SC;
    sc.check();
}