Scale the FPS camera look at vector based on the magnitude of the camera's...

Scale the FPS camera look at vector based on the magnitude of the camera's position, to prevent the rotation being swamped by the position.  

Tested with the problem data from:
http://irrlicht.sourceforge.net/phpBB2/viewtopic.php?t=27958

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@1780 dfc29bdd-3216-0410-991c-e03cc46cb475

source/Irrlicht/CSceneNodeAnimatorCameraFPS.cpp

@@ -158,7 +158,7 @@ void CSceneNodeAnimatorCameraFPS::animateNode(ISceneNode* node, u32 timeMs)
 
 	// set target
 
-	target.set(0,0,100);
+	target.set(0,0,pos.getLength());
 	core::vector3df movedir = target;
 
 	core::matrix4 mat;