Move draw_circle from util.c to gui_util.c

- solidify/util.h, solidify/util.c (draw_circle), solidify/gui_util.h,
  solidify/gui_util.c: moved draw_circle from util.c to gui_util.c
- solidify/util.c: this file is now empty. Remove it.
- solidify/level.c, solidify/overlap.c: include gui_util.h instead of
  util.h
- solidify/Makefile: replace util.o with gui_util.o

solidify/gui_util.h

@@ -0,0 +1,21 @@
+/*
+ * gui_util.h - GUI helper functions
+ *
+ * Written 2009 by Werner Almesberger
+ * Copyright 2009 by Werner Almesberger
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef GUI_UTIL_H
+#define GUI_UTIL_H
+
+#include <gtk/gtk.h>
+
+
+void draw_circle(GdkDrawable *da, GdkGC *gc, int x, int y, int r);
+
+#endif /* !GUI_UTIL_H */