[rbp] Disable textbox autoscrolling while on screensaver.

If the screensaver gets activated while in a view with autoscrolling textboxes,
CPU usage can go as high as 80-85%, the temperature reaches ~71 C.
(This also causes CPUFreq governors such as "conservative" or "ondemand" to always
run at the maximum frequency.)

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Note: I've sent you an e-mail about this a couple days ago - just in case you want more details.
I don't know if you accept pull requests, if you actually want this or if I'm doing it wrong. Feel free to close in that case.
In case this gets merged: feel free to change the commit author and/or date and/or squash as needed.