[gtk] (12 commits) ...Merge branch 'wip/matthiasc/emoji-picker' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  e882db2... build: Make the default setting work on non-Linux Unix-like (*)
  48af688... build: Use cc.links to check linker arguments (*)
  1517114... Fix header guards (*)
  f57c1a2... imcontextxim: Don't assign a variable to itself (*)
  2a87caf... gtk-demo, testgtk: Don't pass an integer to fabs (*)
  3f307c5... wayland: Allow a NULL inhibitors hash table (*)
  e283ed5... Export some entry functions privately (*)
  1104a8f... Add an emoji completion popup (*)
  5d80086... entry: Add emoji completion (*)
  f0f2dd7... widget-factory: add emoji completion to an entry (*)
  8be12a2... Drop Ctrl-Shift-e support (*)
  29d77be... Merge branch 'wip/matthiasc/emoji-picker' into 'master'

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