Fix build with newer gtk+2 (2.20.0).

--- src/Makefile.in.orig	Tue Apr 27 22:45:34 2010
+++ src/Makefile.in	Tue Apr 27 22:45:40 2010
@@ -184,8 +184,7 @@ INCLUDES = \
 	-DPACKAGE_SOURCE_DIR=\"$(srcdir)\" \
 	-DG_DISABLE_DEPRECATED \
 	-DGDK_DISABLE_DEPRECATED \
-	-DGDK_PIXBUF_DISABLE_DEPRECATED \
-	-DGTK_DISABLE_DEPRECATED
+	-DGDK_PIXBUF_DISABLE_DEPRECATED
 
 xdx_SOURCES = \
 	gui.h \
