Fix lua bindings to handle timestamp precision changes

The recent wiretap changes broke the generation of init.lua among other things,
though it did coincidentally fix one of the "yuck" comments in the generator
regex.

(Note that this is entirely untested, because out-of-tree init.lua is and always
has been broken, but it should work)

Change-Id: Id0c27b31c596613997de4ba2f6088eb9d6c8fc53
Reviewed-on: https://code.wireshark.org/review/4361
Reviewed-by: Evan Huus <eapache@gmail.com>