Added missing new interface to irrlicht.h for easier user access.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@1774 dfc29bdd-3216-0410-991c-e03cc46cb475

include/irrlicht.h

@@ -49,6 +49,7 @@
 #include "IQ3LevelMesh.h"
 #include "IAnimatedMeshSceneNode.h"
 #include "IBillboardSceneNode.h"
+#include "IBillboardTextSceneNode.h"
 #include "IBoneSceneNode.h"
 #include "ICameraSceneNode.h"
 #include "IDummyTransformationSceneNode.h"