simplify implementation of dim_vector class Instead of a special style of reference counting (count and number of dimensions both stored in the data array) just use a simple allocated array and define a move constructor and move assignment operator. * dim-vector.h, dim-vector.cc (dim_vector::m_ndims): New data member. Replace all uses of m_rep[-1] with m_ndims. Update constructors to define m_ndims. (dim_vector::chop_trailing_singletons, dim_vector::resize): Simplify. (dim_vector::nil_rep, dim_vector::newrep): Delete static methods. (dim_vector::count, dim_vector::increment_count, dim_vector::decrement_count, dim_vector::clonerep, dim_vector::resizerep, dim_vector::freerep, dim_vector::make_unique): Delete methods and all uses. * jit-typeinfo.h, jit-typeinfo.cc (jit_array::m_ndims): New data member. (jit_array::update): Set m_ndims insetead of accessing from m_dimensions. (octave_jit_end_matrix): Use mat->m_ndims instead of accessing mat->m_dimensions[-1].