Mark unused parameters and set -Wunused-parameter

This allows us to compile with -Wall -Werror in build
environments where -Wall also warns about unused parameters.
Also explicitly set -Wunused-parameter so unused parameters will
cause the build to fail in environments where -Wall does not warn
about them.

Change-Id: Icccf2121d2a9df77b1c224c4976cb9aec56496b3
5 files changed