modernize mxArray class hierarchy * mxarray.in.h: Move mxArray_base class definition here from mex.cc. Don't derive mxArray_base from mxArray. Move all virtual tags from mxArray functions to the corresponding mxArray_base functions. (mxArray_base::as_mxArray): New virtual function. (mxArray::dup): Attempt as_mxArray conversion first. If that succeeds, set name of copy. Othewise, duplicate the rep object. (struct xmxArray): Delete. (mxArray_base::octave_value as_octave_value): Now public. (mxArray_octave_value::octave_value as_octave_value): Now public. (mxArray_number::octave_value as_octave_value): Now public. (mxArray_sparse::octave_value as_octave_value): Now public. (mxArray_struct::octave_value as_octave_value): Now public. (mxArray_cell::octave_value as_octave_value): Now public. (mxArray::mxArray (const xmxArray&)): Delete. (mxArray::mxArray (mxArray_base*, const char*)): Arg is now mxArray_base*, not mxArray*. (mxArray::rep): Now mxArray_base*, not mxArray*. * mex.cc (mxArray_octave_value::dup): Return mxArray_base*, not mxArray*. Don't attempt conversion from octave_value to mxArray here. (mxArray_octave_value::as_mxArray): New function. (mxArray_number::dup): Return mxArray_base*, not mxArray_number*. (mxArray_sparse::dup): Return mxArray_base*, not mxArray_sparse*. (mxArray_struct::dup): Return mxArray_base*, not mxArray_struct*. (mxArray_cell::dup): Return mxArray_base*, not mxArray_dup*.