[mutter] Bump version to 3.21.4

[Florian Müllner <fmuellner src gnome org>]

commit 76175a48d50006cc4e7f631b7494605eeef7cac2
Author: Florian Müllner <fmuellner gnome org>
Date:   Wed Jul 20 11:44:41 2016 +0200

    Bump version to 3.21.4
    
    Update NEWS.

 NEWS         |   20 ++++++++++++++++++++
 configure.ac |    2 +-
 2 files changed, 21 insertions(+), 1 deletions(-)
---
diff --git a/NEWS b/NEWS
index 56f212b..070c8c3 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,23 @@
+3.21.4
+======
+* Fix missing frame border around GTK+ dialogs [Florian; #745060]
+* Improve X11 <-> wayland copy and paste interaction [Carlos; #768007]
+* Add support for NV_robustness_video_memory_purge extension [Rui; #739178]
+* Fix restoring the old focused window on restart [Owen; #766243]
+* Fix fullscreen windows on other monitors stealing focus after closing
+  a window [Rui; #768221]
+* Draw monitor content to individual framebuffer [Jonas; #768976]
+* Provide screen capture API [Jonas; #768978]
+* Misc. bug fixes and cleanups [Rui, Owen, Luca, Olivier, Jonas, Carlos;
+  #767969, #768243, #762407, #767997, #768039, #768977, #768977]
+
+Contributors:
+  Jonas Ådahl, Luca Bruno, Olivier Fourdan, Carlos Garnacho, Rui Matos,
+  Florian Müllner, Owen W. Taylor
+
+Translations:
+  Andika Triwidada [id]
+
 3.21.3
 ======
 * Don't create invalid UTF-8 window description strings [Rui; #765535]
diff --git a/configure.ac b/configure.ac
index 7199094..19ced73 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,7 +2,7 @@ AC_PREREQ(2.62)
 
 m4_define([mutter_major_version], [3])
 m4_define([mutter_minor_version], [21])
-m4_define([mutter_micro_version], [3])
+m4_define([mutter_micro_version], [4])
 
 m4_define([mutter_version],
           [mutter_major_version.mutter_minor_version.mutter_micro_version])