Update metacity to 3.16

Requires compiz to be modified and rebuilt for libmetacity-private changes.

Merge proposal for Compiz:
https://code.launchpad.net/~albertsmuktupavels/compiz/gwd-support-metacity-3-16/+merge/255274

I think this needs to wait until Gtk+ 3.16 lands in wily-release.

I will upload a merge from Debian experimental myself after that (the Debian package has some fixes missing in Robert's commit).

hello devs,
please rebuild compiz to unlock metacity upgrade: the dependencies are available since a while now

This bug was fixed in the package metacity - 1:3.17.2-2ubuntu1

---------------
metacity (1:3.17.2-2ubuntu1) wily; urgency=medium

  [ Robert Ancell ]
  * New upstream release (LP: #1463645)
  * debian/control:
    - Rename libmetacity-private2 to libmetacity-private3,
      following upstream soname bump.
  * debian/libmetacity-private3.symbols:
    - Updated
  * debian/patches/05_raise_on_click_for_click_mode.patch:
  * debian/patches/do_not_use_invalid_back_pixmap.patch:
  * debian/patches/fix_switch_applications.patch:
  * debian/patches/keycode_to_keysym.patch:
  * debian/patches/missing_icon.patch:
  * debian/patches/require_modmask.patch:
    - Applied upstream

  [ Dmitry Shachnev ]
  * Merge with Debian experimental, remaining change:
    - debian/metacity-common.links: Show keybindings in Unity control center.
  * Backport upstream patch to prevent gtk-window-decorator from crashing
    (check_display.diff).

 -- Dmitry Shachnev <email address hidden> Sat, 13 Jun 2015 13:47:40 +0300

This bug was fixed in the package compiz - 1:0.9.12.1+15.10.20150627.1-0ubuntu1

---------------
compiz (1:0.9.12.1+15.10.20150627.1-0ubuntu1) wily; urgency=medium

  [ Alberts Muktupāvels ]
  * Add support for metacity 3.16. (LP: #1463645)

  [ CI Train Bot ]
  * New rebuild forced.

  [ Eleni Maria Stea ]
  * removed unnecessary glClear which causes bug #1462612 (LP: #1462612)

  [ Martin Wimpress ]
  * Tweak the shadows so subtle drop shadows appears on menus, just as
    they do in Macro. Change from Shift Switcher to Static Switcher
    because Shift Switcher is causing Compiz to crash, particularly when
    switching while Steam is running.

  [ Stephen M. Webb ]
  * remove a bashism from the xsession set-profile script (LP: #1460324)

 -- CI Train Bot <email address hidden> Sat, 27 Jun 2015 04:41:51 +0000