[libre-riscv-dev] morphing 6600 code to use power decoder

[Luke Kenneth Casson Leighton]

okaay, i have a first successful - one instruction (an add) -
execution of an "internal op" which is manually placed into the
instruction queue.  adding the POWER decoder in front of that should
be a trivial exercise.

the code's been... messed about somewhat, to get it functional, and
the LDST and Branch Comp Units also need converting.  however the core
out-of-order engine remains exactly the same, so this again should
just be a straightforward exercise.

we do need to write a "proper" Integer ALU - one that uses
PartitionedSignal for operations.  this will be where all the pieces
and hard work that everyone's put in will gel together.

l.