Fix bug which showed up when RTT and text were used in the same scene. I have removed the old RTT checks in 2d methods, and placed a global fix for the texture matrix into the 2d mode setting.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@3500 dfc29bdd-3216-0410-991c-e03cc46cb475