delaunayn: adjust node ordering for positive outward normal vectors (bug #53397) * delaunayn.m: Check sign of simplex volume, flip node order for negative volumes to ensure positive (outward-pointing) normal vectors. Add BISTs to check for positive volumes. * etc/News.8.md: Append function improvement note to delaunayn change paragraph under General Improvements.

## Test duplicate nested function names
function duplicate_nested_function ()

  function r = nested_fcn_1 ()
    r = 1;
  endfunction

  function r = nested_fcn_1 ()
    r = 2;
  endfunction

endfunction