Add LLMotionController* LLMotion::mMotionController

This is needed for synchronization: motions will have to start
(with a specific start time offset) from a point in the code where
only the motion object is available.

I added/used LLMotionController& in a previous commit, this was
now changed into a pointer. There is (obviously) not much reason
for that, but also no disadvantage: the diff relative to LLs code
doesn't get larger since the references where already added, too.

Conflicts:
	indra/llcharacter/llkeyframemotion.cpp
	indra/llcharacter/llkeyframemotion.h

indra/newview/llphysicsmotion.cpp

@@ -314,7 +314,7 @@ void LLPhysicsMotion::getString(std::ostringstream &oss)
 	}
 } 
 
-LLPhysicsMotionController::LLPhysicsMotionController(LLUUID const& id, LLMotionController& controller) : 
+LLPhysicsMotionController::LLPhysicsMotionController(LLUUID const& id, LLMotionController* controller) :
         AIMaskedMotion(id, controller, ANIM_AGENT_PHYSICS_MOTION),
         mCharacter(NULL),
 		mIsDefault(true)