x86: correct / adjust debug printing

x86: correct / adjust debug printing

For quite some time we've been using combinations of bits for
specifying various registers in operands and templates. I think it was
Alan who had indicated that likely the debug printing would need
adjustment as a result. Here we go.

Accumulator handling for GPRs gets changed to match that for FPU regs.
For this to work, OPERAND_TYPE_ACC{32,64} get repurposed, with their
original uses replaced by direct checks of the two bits of interest,
which is cheaper than operand_type_equal() invocations.

For SIMD registers nothing similar appears to be needed, as respective
operands get stripped from the (copy of the) template before pt() is
reached.

The type change on pi() is to silence a compiler diagnostic. Arguably
its other parameter could also be const-qualified.