Add target to Generate depend.png

Makefile

@@ -2,6 +2,8 @@ PREFIX=/usr/local
 RM=rm -f
 MKDIR=mkdir -p
 
+.PHONY: all test check doc clean distclean depend depend.png install
+
 all:
 	@echo "Nothing to be done."
 
@@ -18,7 +20,7 @@ clean:
 	cd tests && $(MAKE) clean
 	cd example && $(MAKE) clean
 	cd bench && $(MAKE) clean
-	$(RM) -f README.html
+	$(RM) -f README.html depend.dot
 
 distclean:
 	cd tests && $(MAKE) distclean
@@ -26,6 +28,10 @@ distclean:
 depend:
 	cd tests && $(MAKE) depend
 
+depend.png:
+	(echo "digraph g { " ; for i in *.h ; do list=$$(grep "include \"" $$i |cut -f2 -d\") ; for j in $$list ; do echo "\"$$i\" -> \"$$j\" ;" ; done ; done ; echo "}" )> depend.dot
+	dot -Tpng depend.dot -o depend.png
+
 install:
 	$(MKDIR) $(DESTDIR)$(PREFIX)/include
 	cp m-*.h $(DESTDIR)$(PREFIX)/include