Add functionality to stop and reenable the automatic scrolling of the text.

[jpsachse]

I've added three functions to stop and reenable the automatic scrolling feature.

This is useful, when the label is out of view for some time. Otherwise, it might become visible and the text is scrolled to an arbitrary position.

[cbess]

Interesting. I'll review the code.

[delannoyk]

Would love to see this feature coming!

[jpsachse]

Is there anything that prevents you from merging this (by now) quite old pull request that I could resolve?

[cbess]

Compared to other things I'm working on, this has low priority. Thanks for pinging me about it. I will make time to review/merge it this weekend.

[cbess]

Also, from my initial review, a while back, I realized that I will have to rewrite your API. I think the API and naming of the proposed methods could be better. But, I will adopt most of the underlying logic. Thanks for the code.

[jpsachse]

Okay, no worries :-)