add DisplayLink driver V2.1 (requires #3422)

[pedros]

No description provided.

[pedros]

The commented-out lines are there for review. This pkg contains an app bundle for performing uninstalls, however I can't make it be non-interactive; it pops up a dialogue box asking for confirmation.

Since I don't know to what extent the :pkgutil directive will remove components, I added all IDs in the payload that I could find.

[rolandwalker]

Great! I'm so glad to see this contribution.

:pkgutil can only accept multiple arguments since a few days ago in #3217, but I think that's OK, because this Cask could not be merged before the next code release.

The uninstaller app runs an Applescript at DisplayLink Software Uninstaller.app/Contents/Resources/Scripts/Uninstaller.scpt. Unfortunately, the vendor has compiled it in such a way that osadecompile 'DisplayLink Software Uninstaller.app/Contents/Resources/Scripts/Uninstaller.scpt' does not reveal anything to us.

[rolandwalker]

Oh, we forgot to merge this after #3422? That code has been in release for a couple of weeks at least. Can you squash these commits?