polygons2d/polygonArea.m: revert to previous version and adapt for polygons with holes
polygons2d/polygonArea.m: revert to previous version and adapt for polygons with holes

there were some problems with nested loops.
I have kept doc updates, with adaptation, as Matlab do not accept "a = b = c" statements.

dlegland/matGeom,dlegland/matGeom,kakila/matGeom,kakila/matGeom