Fix warnings about "unused" parameters and typedefs.

CLang and recent GCC warn about the "typedef" `OneColInt` in `AutoDiffHelpers.hpp` being unused.  Similarly, GCC warns about unused parameters in various place at level `-Wunused`.  This change-set either removes (`OneColInt`) or suppresses those messages.

This is a first step towards removing the most egregious transgressions at http://www.opm-project.org/CDash/viewBuildError.php?type=1&buildid=6039.