Implement a programmatic cancel of an updpate

[gaidarjimax]

Hello! I am using Sparkle, more specific the SPUUpdater, to update another application. I would like to have an option to cancel an update programmatically when automaticallyDownloadsUpdates is set to true, and SPUAutomaticUpdateDriver is performing the update.

Possible Fix

The SPUAutomaticUpdateDriver as other SPUUpdateDrivers has abortUpdateWithError method which does exactly what I need, but this method is not reachable from the SPUUpdater interface, or from UserDriver, or the UpdaterDelegate that are passed to the SPUUpdater.

Thank you!