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 subfunctions
function x = duplicate_subfunction ()
  x = 1;
endfunction

function y = duplicate_subfcn_1 ()
  y = 2;
endfunction

function z = duplicate_subfcn_1 ()
  z = 3;
endfunction