[mutter] Bump version to 3.21.91

[Florian Müllner <fmuellner src gnome org>]

commit 335764e815e94a7ce5d21803578ec3038930789c
Author: Florian Müllner <fmuellner gnome org>
Date:   Tue Aug 30 00:27:02 2016 +0200

    Bump version to 3.21.91
    
    Update NEWS.

 NEWS         |   19 +++++++++++++++++++
 configure.ac |    2 +-
 2 files changed, 20 insertions(+), 1 deletions(-)
---
diff --git a/NEWS b/NEWS
index 6c7a0b2..0d15406 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,22 @@
+3.21.91
+=======
+* Add support for xdg-foreign protocol [Jonas; #769786]
+* Support monitor rotation on wayland [Carlos; #745079]
+* Port xdg-shell implementation to unstable v6 [Jonas; #769936]
+* Handle unsupported buffer sizes more gracefully [Olivier; #770387]
+* Use the same output naming logic as the X server on wayland [Rui; #770338]
+* Fix replies in gnome-shell's chat notifications on wayland [Florian; #758167]
+* Misc. bug fixes and cleanups [Bastien, Sjoerd, Jonas; #769276, #769636,
+  #770131, #770324, #769731]
+
+Contributors:
+  Jonas Ådahl, Olivier Fourdan, Carlos Garnacho, Rui Matos, Florian Müllner,
+  Bastien Nocera, Sjoerd Simons
+
+Translations:
+  Piotr Drąg [pl], Mario Blättermann [de], Andika Triwidada [id],
+  Enrico Nicoletto [pt_BR], Мирослав Николић [sr, sr@latin]
+
 3.21.90
 =======
 * Consider XDG_SESSION_TYPE when determining session type [Jouke; #759388]
diff --git a/configure.ac b/configure.ac
index 9fc9868..711cade 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], [90])
+m4_define([mutter_micro_version], [91])
 
 m4_define([mutter_version],
           [mutter_major_version.mutter_minor_version.mutter_micro_version])