updating with newer version of cgf.go.  Adding checks to check for
  - bounds of ABV vectors when found (compared to StepPerPath)
  - makes sure an OverflowMap entry exists if it appears as an overflow
    in the ABV vector
  - makes sure the entry appears as an overflow entry in the ABV vector
    if it appears in the OverflowMap
bug fix: overflow entries of variable length weren't always stored
  in the overflow map properly.  fixed.