Test that creating an s batch file with -bsaves works

It might fail, for example with "Error, -bsaves makes sense in batch mode only"
error, and then all following tests also exhibit that error - which is not
detected, because those tests are expected to return an error code.

test.ecm

@@ -324,7 +324,7 @@ fi
 
 # exercise batch error messages...
 TEST=test.ecm.s$$
-$ECM -bsaves $TEST 11e3 < ${GMPECM_DATADIR}/c155
+$ECM -bsaves $TEST 11e3 < ${GMPECM_DATADIR}/c155; checkcode $? 0
 $ECM -bloads $TEST 1000 < ${GMPECM_DATADIR}/c155; checkcode $? 1
 $ECM -bloads $TEST 10900 < ${GMPECM_DATADIR}/c155; checkcode $? 1
 /bin/rm -f $TEST