Don't give names to parameters you don't use.

C++, unlike C, lets you do that.  This squelches warnings from MSVC++.

Change-Id: Id7127392b7690769111afdb951951d743f1d5e63
Reviewed-on: https://code.wireshark.org/review/4019
Reviewed-by: Guy Harris <guy@alum.mit.edu>