sites plus optimized constant code a bit (one less register
  used).
- changed conditional branches, might need a re-tweak later
- gave up on agen OINDEX and copied/fixed the version in 8g

go/test: passes 66% (225/339)

R=rsc
APPROVED=rsc
DELTA=148  (67 added, 32 deleted, 49 changed)
OCL=35040
CL=35055