Public domain version of the Korn shell

Formula was removed
Last version was:

Homepage: https://www.cs.mun.ca/~michael/pdksh/

Formula history

Zhiming Wang pdksh: migrate to boneyard (#7601)
Viktor Szakats pdksh: use secure urls
Mike McQuaid Rename patches repository to formula-patches.
Dominyk Tiller formulae: migrate patches (part 2)
Nikolaus Wittenstein Add descriptions to all remaining homebrew packages
Geoff Nixon pdksh: patches + fixed install name
Jack Nagel pdksh: use checksummed patches