Added support for standard vertices, if no lightmaps are used. This saves lots of of memory and update times. But it needs some more testing, because I have not enough test files. Moreover, I've added some speedup for the vertex position loading with heavily reduced parsing efforts.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2488 dfc29bdd-3216-0410-991c-e03cc46cb475