[gimp] Bump required GTK+ version to 2.18.1

[Martin Nordholts <martinn src gnome org>]

commit 15f86a80ac758542e5899a9e25944e5a1b85691e
Author: Martin Nordholts <martinn src gnome org>
Date:   Sat Oct 17 14:32:37 2009 +0200

    Bump required GTK+ version to 2.18.1
    
    Bump required GTK+ version to 2.18.1 so we get
    e.g. gtk_widget_set_visible() and offscreen widget hierarchies. So far
    we don't rely on bug fixes in any later releases.

 INSTALL      |    2 +-
 configure.ac |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/INSTALL b/INSTALL
index 113551d..2906e88 100644
--- a/INSTALL
+++ b/INSTALL
@@ -43,7 +43,7 @@ header files installed.
        git://git.gnome.org/babl
        git://git.gnome.org/gegl
 
-  4. You need to have installed GTK+ version 2.16.6 or newer.
+  4. You need to have installed GTK+ version 2.18.1 or newer.
      GIMP also need a recent versions of GLib (>= 2.20.0) and
      Pango (>= 1.20.1). Sources for these can be grabbed from
      ftp://ftp.gtk.org/.
diff --git a/configure.ac b/configure.ac
index 1cceddf..2784030 100644
--- a/configure.ac
+++ b/configure.ac
@@ -43,7 +43,7 @@ m4_define([gimp_full_name], [GNU Image Manipulation Program])
 m4_define([babl_required_version], [0.1.0])
 m4_define([gegl_required_version], [0.1.0])
 m4_define([glib_required_version], [2.20.0])
-m4_define([gtk_required_version], [2.16.6])
+m4_define([gtk_required_version], [2.18.1])
 m4_define([gdk_pixbuf_required_version], [gtk_required_version])
 m4_define([cairo_required_version], [1.6.0])
 m4_define([pangocairo_required_version], [1.20.1])