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.

void main()
{
  void foo() {}

  auto dg = &foo;

  if(dg.funcptr is null)
  { assert(0); }
}