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.
Merge pull request #37 from bska/Wunused

Fix warnings about "unused" parameters and typedefs.