Adds a new test checking conditional branch BO values.
* testsuite/gas/ppc/bc.s,
* testsuite/gas/ppc/bcat.d,
* testsuite/gas/ppc/bcaterr.d,
* testsuite/gas/ppc/bcaterr.l,
* testsuite/gas/ppc/bcy.d,
* testsuite/gas/ppc/bcyerr.d,
* testsuite/gas/ppc/bcyerr.l: New tests.
* testsuite/gas/ppc/ppc.exp: Run them.