lua output doc: Use more descriptive variable names in the examples

lua output doc: Use more descriptive variable names in the examples

This also removes the "args" parameter of the hooking functions in the examples,
since this parameter is unused in all functions.
It would not be very helpful anyways since 3 of the 4 functions don't get passed
any parameters. The only exception is init() which gets a table containing:
  script_api_ver = 1