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/llcharacter/llkeyframefallmotion.cpp

@@ -49,7 +49,7 @@
 // LLKeyframeFallMotion()
 // Class Constructor
 //-----------------------------------------------------------------------------
-LLKeyframeFallMotion::LLKeyframeFallMotion(const LLUUID &id) : LLKeyframeMotion(id)
+LLKeyframeFallMotion::LLKeyframeFallMotion(LLUUID const& id, LLMotionController* controller) : LLKeyframeMotion(id, controller)
 {
 	mVelocityZ = 0.f;
 	mCharacter = NULL;