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 tuple1;

template Tuple(T...) {
    alias T Tuple;
}

struct S
{
    int i;
    long l;
}

void main()
{
    S s = S(Tuple!(1,2L));
    assert(s.i == 1);
    assert(s.l == 2);
}