Auto-scrolling fix for Catalina - pull request review

[Robert Vehse]

Hi everyone,

In my email regarding codesigning from two days ago I mentioned work being done to fix an issue with auto-scrolling on Catalina.

Pull requests have now been created:
- https://bitbucket.org/adium/adium/pull-requests/11 "Update JVMarkedScroller to use public APIs to determine scroller direction"
- https://bitbucket.org/adium/adium/pull-requests/12 "Adjust auto-scroll code to use more compatible APIs, adding support for macOS Catalina"

It would be great if someone could review the changes.

Cheers,
Robbie