Since the taxonomy is now a real C++ struct with constructor
and destructor, dive_site has to be converted to C++ as well.
A bit hairy for now, but will ultimately be distinctly simpler.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
The undo-code uses owning pointers based on std::unique_ptr to
manage lifetime of C-objects. Since these are generally useful,
move them from the undo-code to the core-code. In fact, this
eliminates one instance of code duplication.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
