lots of debugging of predication, found other errors

lots of debugging of predication, found other errors

lots of stuff here:
* changed sv reg and pred entry layout to make them a bit more
  human-readable: put the key and idx on byte-boundaries
* bug in SV REG setting (getting int table instead of fp one, twice)
* bug(s) in SV PRED table setting (zeroing the reg tables, using idx not
  key and more)
* stop lookup of predication if the *REGISTER* entry is inactive
  (but not if it is a scalar, because scalar predication is ok)
  this was the final piece of the puzzle that got predication working
* added a useful macro for creating SV REG and PRED CAM table entries

predication now working including zeroing