rather big change to interaction between regfile and compunits on read

rather big change to interaction between regfile and compunits on read
regfiles are now sync-delayed by one clock from "ren".  this means that
a read-request has to be fired off then excluded from the PriorityPicker,
whilst waiting for the output to arrive on the next clock.  *then*
the "go read" signal can be fired, which gets the data (arriving 1 cycle
late from the regfile) "in sync" with its "go read"