[gtk] (7 commits) ...Merge branch 'matthiasc/for-master' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  312289f... docs: Mention <packing> in migration guide (*)
  4c9bd6e... wayland: Add a comment (*)
  e437c55... Add a doc comment for gsk_rounded_rect_is_circular (*)
  8f95661... Clean up some comments (*)
  a459856... icontheme: Add detail to the 'not found' message (*)
  ff87431... Merge branch 'master' into 'matthiasc/for-master' (*)
  74a41ee... Merge branch 'matthiasc/for-master' into 'master'

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