[gtkmm] Created tag 3.21.2

[Murray Cumming <murrayc src gnome org>]

The unsigned tag '3.21.2' was created.

Tagger: Murray Cumming <murrayc murrayc com>
Date: Mon May 30 10:37:18 2016 +0200

    3.21.2

Changes since the last tag '3.20.0':

Kjell Ahlstedt (16):
      Gtk::GLArea: Fix refcount in signal_create_context()
      Gtk::GLArea: Better fix of refcount in signal_create_context()
      Gdk::Window::create_gl_context(): Remove refreturn
      Gtk::TreeView::unset_rows_drag_dest(): Fix the documentation
      Gdk::Display, Gdk::Visual: Deprecate methods which are deprecated in gtk+
      Fix "make check" after deprecations
      ButtonBox demo: Enable mnemonics in the buttons
      HeaderBar demo: Use the pan-start-symbolic and pan-end-symbolic icons
      Gdk::DeviceManager docs: Superseded by Gdk::Seat
      Gdk: Regenerate docs.xml and .defs files
      Add Gdk::Monitor
      Gdk::Display: Add methods and signals related to Gdk::Monitor
      Gdk::Device: Add get_axes(), signal_changed() and many properties
      Gdk::GLContext: Add set/get_use_es()
      Gtk: Regenerate gtk_docs.xml and .defs files
      Gtk::Clipboard, GLArea, ShortcutsShortcut: Add new methods and properties

Murray Cumming (8):
      C++11: generate_cellrenderer(): Use auto.
      C++11: Deprecate operator void*(), replacing them with explicit operator bool().
      TreeView: _auto_store_on_cellrenderer_text_edited_numerical():
      Slight whitespace change.
      NEWS: Minor correction.
      PrintSettings: Make create_*() from public, not protected.
      Remove trailing whitespace.
      3.21.2