[metacity] bump GTK+ required version

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 3671752a98698e8be3bec8fd742a31dbe30cdd7c
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Thu Oct 29 13:37:05 2015 +0200

    bump GTK+ required version
    
    gtk_widget_path_iter_set_object_name was added in version 3.19.1.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 9845ecc..e10ca7c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -82,7 +82,7 @@ AC_CHECK_SIZEOF(__int64)
 ## byte order
 AC_C_BIGENDIAN
 
-GTK_MIN_VERSION=3.15.2
+GTK_MIN_VERSION=3.19.1
 GIO_MIN_VERSION=2.25.10
 CANBERRA_GTK=libcanberra-gtk3