removed 'unused parameter' warnings

This is a small fix of warnings "unused parameter" thrown by clang and g++ when -Wextra (maybe already with -Wall) is set. The warning addresses the issue that in a function some parameters with a name are not used within the function body. Sometimes this is intended (to just change the function signature), but sometimes this indicates a missing functionality or an interface design that needs improvements.

I have commented out the parameter name so that it acts as a documentation of the function argument instead.