* Remove dead function is_point_on_page() - unused since c99ca9ca.

* Remove block_updates preference - unhelpful since e728110b.

* Forward port pinch zoom changes from 258bfc22, specifically "Remove
  the redundant last_mouse tracking by the desktop, and guard against
  the mouse not being over the canvas during a pinch zoom gesture".

* Remove spurious gtk4 commas from framecheck output.

* Fix lambda default-capture warnings.