[gtk] (9 commits) ...Merge branch 'preedit-selection-fix' into 'master'

[Matthias Clasen <matthiasc src gnome org>]

Summary of changes:

  4b9aeaf... imcontext: Add [gs]et_surrounding_with_selection (*)
  97db959... immulticontext: Implement [gs]et_surrounding_with_selection (*)
  35fceca... imwayland: Pass anchor with surrounding (*)
  feccdad... text: Send anchor with surrounding (*)
  447203c... text: Delete selection when preedit starts (*)
  ccae0e1... text: Optimize away 0-change insertions and deletions (*)
  d1fbfb9... textview: Send anchor with surrounding (*)
  d28df0b... textview: Delete selection when preedit starts (*)
  c303ec1... Merge branch 'preedit-selection-fix' into 'master'

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