New NOCROSSREFS_TO tests

[Matthew Fortune]

Alan Modra <amodra@gmail.com> writes:
> Fixes failures on hppa-linux and alpha-linux due to not merging
> .data.* and .sdata into .data.  cross3.t modified too since it is the
> template for the NOCROSSREFS_TO scripts.

Thanks Alan. I had a concern about this and forgot to raise it. The
tests that are expected to produce no warnings are dependent on the
correct sections being merged which could depend on compiler options.
It will be all too easy to spuriously pass but hopefully the tests
that check for failure will pick up any non-standard section uses.

Matthew