[gcr] build: Require gtk+ >= 3.12

[Stefan Walter <stefw src gnome org>]

commit ba6c98498db2a8c3af0dba8c0db4396007127ff6
Author: Alexandre Rostovtsev <tetromino gentoo org>
Date:   Wed Jul 29 08:20:40 2015 -0400

    build: Require gtk+ >= 3.12
    
    https://bugzilla.gnome.org/show_bug.cgi?id=753016

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 7913742..824de3b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -17,7 +17,7 @@ GLIB_MAX=GLIB_VERSION_2_38
 
 GCRYPT_VERSION=1.4.5
 
-GTK_REQ=3.10
+GTK_REQ=3.12
 
 dnl ****************************************************************************
 dnl Library package and libtool versioning