2.5 - Rotation order is now taken into account for constraints

* Added a 'rotOrder' parameter for constraint evaluation objects and constraint targets, which describes the rotation mode used for the matrices there. 

Todos:
* Constraint targets default to using XYZ only for now. This will need be be addressed eventually.
* Copy Rotation constraint currently cannot use the new rotation order code for the target matrix. What's surprising is that even though it's just using XYZ as the old code did, it doesn't work, and yet everything else works nicely. Silly constraint! (it is almost impossible to improve this constraint further without breaking a rig out there)

source/blender/blenkernel/BKE_constraint.h

@@ -49,6 +49,7 @@ typedef struct bConstraintOb {
 	float startmat[4][4];		/* original matrix (before constraint solving) */
 	
 	short type;					/* type of owner  */
+	short rotOrder;				/* rotation order for constraint owner (as defined in eEulerRotationOrders in BLI_arithb.h) */
 } bConstraintOb;
 
 /* ---------------------------------------------------------------------------- */