Add a clean target to main Makefile

Makefile

@@ -15,4 +15,8 @@ sqprof:
 sq64:
 	cd squirrel; $(MAKE) sq64
 	cd sqstdlib; $(MAKE) sq64
-	cd sq; $(MAKE) sq64
+	cd sq; $(MAKE) sq64
+	
+clean:
+	rm lib/*
+	rm bin/*