Handle clamping by just ensuring visibility
Handle clamping by just ensuring visibility

Still does weird things with long messages, but it seems a little better? I'm
not sure. Test with two long messages in a row. Previously there were cases
when the selection was invisible.

This might argue for a more drastic departure from BarnOwl's behavior. BarnOwl
is really really bad at long messages.

Smooth scroll might also help.

roost-im/roost,roost-im/roost