Merged from 1.5 branch revisions 2333:2347. Fix depthbuffer under d3d, renderstates under OpenGL, stencilshadow under OpenGL.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2349 dfc29bdd-3216-0410-991c-e03cc46cb475