Update and rename demo_dynamic.py3 to demo_dynamic.py

this version runs under python2 and python3 so only one version need be distributed

Author: buggywhip

demos/demo_dynamic.py3 demos/demo_dynamic.pydemos/demo_dynamic.py3 renamed to demos/demo_dynamic.py

@@ -1,7 +1,7 @@
 
 
 """
-    demo_dynamic.py3                                    v2b
+    demo_dynamic.py                                    v2b
 
     This program demonstrates Python's use of the dynamic
     language support additions to LTC, namely access to LTC