s390x/tcg: Implement VECTOR PACK *

s390x/tcg: Implement VECTOR PACK *

This is a big one. Luckily we only have a limited set of such nasty
instructions.

We'll implement all variants with helpers, except when sources and
the destination don't overlap for VECTOR PACK. Provide different helpers
when the cc is to be modified. We'll return the cc then via env->cc_op.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20190307121539.12842-20-david@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>