Avoids lots of const casts and there shouldn't be a good reason to have those non-const.
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6396 dfc29bdd-3216-0410-991c-e03cc46cb475
Before it crashed when index-count wasn't a multiple of 3, now it just doesn't create the last triangle then.
git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6110 dfc29bdd-3216-0410-991c-e03cc46cb475