[Code clean] Unused variables

[sbryngelson]

The following is the output from looking for -Wunused-variable appending to the GNU compile options. Not all of these have to be resolved, and some shouldn't be because they are required, but many are problematic.

This can be added to CI as a measure of code cleanness by checking for the number of these warnings.

See attached .txt file

clean-unused-variable.txt