Log Message:
(check-cvs-diff)
- Add Usage
- Rename FILE handle FILE to CVS_DIFF
- Add STDERR for error reporting
- Hardcoded /usr/pkgsrc revised to use PKGSRCDIR

(replace-commonbump)
- Try to show where we have "Don't know how to make ..." message
  (but still failing)
- Revise Error Message when  ${VARNAME} is empty.