[gnome-system-monitor] Bump gtkmm version requirement for Gtk::Application and Gtk::ApplicationWindow APIs added in 3.3.18.

[Robert Roth <robertroth src gnome org>]

commit fec4913f436c503bd5392cb1d2cf16607826a9c2
Author: Robert Roth <robert roth off gmail com>
Date:   Thu Sep 27 23:24:08 2012 +0300

    Bump gtkmm version requirement for Gtk::Application and
    Gtk::ApplicationWindow APIs added in 3.3.18.

 configure.ac |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 74432ae..fc9f990 100644
--- a/configure.ac
+++ b/configure.ac
@@ -32,7 +32,7 @@ LIBWNCK_REQUIRED=2.91.0
 LIBGTOP_REQUIRED=2.28.2
 GTK_REQUIRED=3.0
 GNOME_ICON_THEME_REQUIRED=2.31
-GTKMM_REQUIRED=2.99
+GTKMM_REQUIRED=3.3.18
 GIOMM_REQUIRED=2.27
 GLIBMM_REQUIRED=2.27
 LIBXML_REQUIRED=2.0