[gtk/matthiasc/for-master] (7 commits) ...x11: Avoid a critical in clipboard data transfer

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  694daa1... Move print-editor to demos (*)
  c133db4... Drop the gtkgears test (*)
  e7bf4a3... tests: Move testcairo into gtk4-demo (*)
  fe6238d... tests: Drop the visuals test (*)
  a4debec... Merge branch 'tests-cleanup' into 'master' (*)
  9c13bf7... Merge branch 'matthiasc/for-master' into 'master' (*)
  7a427a7... x11: Avoid a critical in clipboard data transfer

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