In s390_decode_and_irgen don't divert the default case to a decoding error.
That's wrong as the default case is never supposed to occur.

In disInstr_S390_WRK use vpanic for the default case for sake of consistency.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2952 8f6e269a-dfd6-0310-a8e1-e2731360e62c