FTL_PSUBPP: Parameter substitution corruption involving PPs (pdksh)
FTL_PSUBPP: Parameter substitution corruption involving PPs (pdksh)

bin/modernish:
- Add FTL_PSUBPP to detect a bug in pdksh: if a parameter
  substitution of type #, %, ##, %% modifies a positional
  parameter using a pattern containing another positional
  parameter, the result is corrupted.

modernish/modernish