[imcc] change emit_pbc !ins->op warnings to fatal again
[imcc] change emit_pbc !ins->op warnings to fatal again

closing GH #1039
all ops treated by -O2 constant propagation are now properly set

youprofit/parrot,tkob/parrot,FROGGS/parrot,youprofit/parrot,parrot/parrot,tkob/parrot,tkob/parrot,tkob/parrot,parrot/parrot,youprofit/parrot,FROGGS/parrot,youprofit/parrot,FROGGS/parrot,parrot/parrot,youprofit/parrot,youprofit/parrot,tkob/parrot,FROGGS/parrot,youprofit/parrot,youprofit/parrot,parrot/parrot,FROGGS/parrot,tkob/parrot,FROGGS/parrot,FROGGS/parrot,tkob/parrot,tkob/parrot,parrot/parrot,FROGGS/parrot