[duim,gtk] Don't emit a signal when the scrollbar's adjustment changes

This doesn't seem to be needed anymore, see:
https://developer.gnome.org/gtk3/3.5/GtkAdjustment.html#GtkAdjustment-changed
[duim,gtk] Update grab-pointer and ungrab-pointer
[duim,gtk] Use cairo functions in establish-pen
Merge pull request #539 from fracek/duim-gtk-fixes-2

Duim gtk fixes 2