Bugfix for FBX export for animations

in 2.48 constant interpolations meant that wasnt a problem but since it now uses linear interp. you can notice errors with animated characters because the 2 eulers are not compatible.

Added optional euler_compat argument to matrix.toEuler(eul) and quat.toEuler(eul) so when getting the euler rotations from a list of matrices the animation curve will be continues.
Also added euler.makeCompatible(euler).

- warning silenced for imagepaint.c

source/blender/python/api2_2x/doc/Mathutils.py

@@ -617,6 +617,12 @@ class Euler:
     @rtype: Quaternion object
     @return: Quaternion representation of the euler.
     """
+  def makeCompatible(eul_compat):
+    """
+    Make this euler compatible with another, so interpolating between them works as expected.
+    @rtype: Euler object
+    @return: an instance of itself
+    """
 
 class Quaternion:
   """
@@ -718,9 +724,11 @@ class Quaternion:
     @return: an instance of itself
     """
 
-  def toEuler():
+  def toEuler(eul_compat):
     """
     Return Euler representation of the quaternion.
+    @type eul_compat: L{Euler}
+    @param eul_compat: Optional euler argument the new euler will be made compatible with (no axis flipping between them). Useful for converting a series of matrices to animation curves.
     @rtype: Euler object
     @return: Euler representation of the quaternion.
     """
@@ -870,9 +878,11 @@ class Matrix:
     @return: an instance of itself.
     """
   
-  def toEuler():
+  def toEuler(eul_compat):
     """
     Return an Euler representation of the rotation matrix (3x3 or 4x4 matrix only).
+    @type eul_compat: L{Euler}
+    @param eul_compat: Optional euler argument the new euler will be made compatible with (no axis flipping between them). Useful for converting a series of matrices to animation curves.
     @rtype: Euler object
     @return: Euler representation of the rotation matrix.
     """