[gtksourceviewmm] Created tag 3.12.0

[Murray Cumming <murrayc src gnome org>]

The unsigned tag '3.12.0' was created.

Tagger: Murray Cumming <murrayc murrayc com>
Date: Wed May 6 09:17:30 2015 +0200

    3.12.0

Changes since the last tag 'gtksourceviewmm-3.2.0':

Murray Cumming (9):
      Add #includes needed with the latest glibmm.
      Examples: Do not include gmessages.h directly.
      Tests: Use Gtk::Application instead of Main.
      Fix an error in the previous commit
      Deprecate some methods because the corresponding C functions were deprecated.
      Deprecate more (deprecated in the C API) API.
      Update Doxyfile.in
      3.12.0
      Update NEWS