support HISTCONTROL=ignoredups

Is it not an issue with KSHbut it will be nice if KSH support "ignore duplicates" .
Thank you

[McDutchie]

This repo is not being developed any more because AT&T abandoned ksh. However, ksh development continues at https://github.com/ksh93/ksh - that repo is now the basis of the latest ksh versions in most (?) Linux and BSD distributions. And I agree this would be nice to have. I'll file this there as a feature request.