wireshark: add copyright to output file

This must be GPLv2 because it uses Wireshark APIs.

http://ask.wireshark.org/questions/1059/license-of-dissectors-written-in-lua
diff --git a/wireshark_gen/templates/openflow.lua b/wireshark_gen/templates/openflow.lua
index 243157a..dac110a 100644
--- a/wireshark_gen/templates/openflow.lua
+++ b/wireshark_gen/templates/openflow.lua
@@ -1,6 +1,6 @@
 :: import of_g
 :: ir = of_g.ir
--- TODO copyright (GPL)
+:: include('_copyright.lua')
 
 :: include('_ofreader.lua')