Fix origin returned by IQM's LerpTag

It use to return pose joint's offset from base at the lerped frame, now it returns the joint's origin at the lerped frame.

Patch by Axel Isouard and Zack Middleton.

code/renderergl1/tr_local.h

@@ -649,6 +649,7 @@ typedef struct {
 	int		*triangles;
 
 	int		*jointParents;
+	float		*jointMats;
 	float		*poseMats;
 	float		*bounds;
 	char		*names;