[lua, tcpheader] Fixes for #4521

[kaby76]

This PR fixes #4521.

For lua, I updated the stat.lua.trq file in the examples, correcting the expected count of stat nodes in the parse tree.

The rest of the numerous changes are for tcpheader, which requires file encodings for parsing. This required a change in trgen to extract new information from the desc.xml file. I added the Go target for the grammar. I will need to update the desc.xsd file with this information but will do so in another PR.

PR incomplete: I need to update the templates for all targets.