[gtk] (17 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  fd63193... transition demo: Make buttons symbolic (*)
  5829bc7... Use correct child widget when measuring (*)
  fd1e8af... meson: Change introspection option to yielding feature (*)
  dfd16e3... ci: Use a newer meson in images (*)
  517a840... ci: Use the v24 images (*)
  7780b89... ci: Really enable werror (*)
  21c8bc2... build: Require meson 0.54 (*)
  b0da095... gsk: Fix compiler warnings (*)
  72eb89e... gtk-demo: Add the shader paintable sources (*)
  b936419... ci: Remove --fatal-meson-warnings (*)
  103080c... build: Remove an unneeded version check (*)
  91c8f6b... build: Try to fix docs+subprojects (*)
  9bac129... ci: Try to get everything building again (*)
  6e7c0ce... ci: Give up on sysprof for now (*)
  028cd1e... Revert "Fix the build with cups < 2.3" (*)
  cbe3de9... Merge branch 'master' into 'matthiasc/for-master' (*)
  ce29545... Merge branch 'matthiasc/for-master' into 'master'

(*) This commit already existed in another branch; no separate mail sent