Fixed gtkmm to not try to install documentation if no doxygen is available

gtk+/gtkmm/gtkmm.conf

@@ -2,7 +2,7 @@
 # This copyright note is auto-generated by ./scripts/Create-CopyPatch.
 #
 # Filename: package/.../gtkmm/gtkmm.conf
-# Copyright (C) 2006 The OpenSDE Project
+# Copyright (C) 2006 - 2008 The OpenSDE Project
 # Copyright (C) 2004 - 2006 The T2 SDE Project
 #
 # More information can be found in the files COPYING and README.
@@ -16,4 +16,6 @@
 var_append confopt ' ' "--disable-examples"
 var_append confopt ' ' "--disable-demos"
 
-
+if ! pkginstalled doxygen; then
+	var_append extraconfopt ' ' '--disable-docs'
+fi