Fix cursor problems found by buffer and by rvl2 as described in http://irrlicht.sourceforge.net/phpBB2/viewtopic.php?t=34823&highlight=


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2669 dfc29bdd-3216-0410-991c-e03cc46cb475