[clutter] Bump up requirement for Cogl

[Emmanuele Bassi <ebassi src gnome org>]

commit f5409ecd3a28a9e32467652d34120aa77fcff0a2
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Fri Aug 21 11:57:59 2015 +0100

    Bump up requirement for Cogl
    
    We're going to use API added in Cogl 1.21.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 259f70f..01f666c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -137,7 +137,7 @@ AC_HEADER_STDC
 
 # required versions for dependencies
 m4_define([glib_req_version],           [2.44.0])
-m4_define([cogl_req_version],           [1.20.0])
+m4_define([cogl_req_version],           [1.21.2])
 m4_define([json_glib_req_version],      [0.12.0])
 m4_define([atk_req_version],            [2.5.3])
 m4_define([cairo_req_version],          [1.14.0])