[gtksourceview] (10 commits) ...Style schemes: add heading styles in comments

[Sébastien Wilmet <swilmet src gnome org>]

Summary of changes:

  041e1a9... Completion: weak reference to the view (*)
  58f500c... Revert "Prevent construction of completion after dispose ha (*)
  5765364... Completion: support changing the view's buffer (*)
  3d5a9f4... Completion: override constructed (*)
  0e563c5... Completion: move the code so the prototype is not needed (*)
  eb1d172... Keep interactive completion blocked when buffer changes (*)
  fe409df... Doc: section about default style schemes
  0d683ef... Doc: custom context classes can be used
  511472d... Doc: no "current match" concept for the search and replace
  6915a7d... Style schemes: add heading styles in comments

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