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/euler.h

@@ -58,6 +58,7 @@ PyObject *Euler_Unique( EulerObject * self );
 PyObject *Euler_ToMatrix( EulerObject * self );
 PyObject *Euler_ToQuat( EulerObject * self );
 PyObject *Euler_Rotate( EulerObject * self, PyObject *args );
+PyObject *Euler_MakeCompatible( EulerObject * self, EulerObject *value );
 PyObject *Euler_copy( EulerObject * self, PyObject *args );
 PyObject *newEulerObject( float *eul, int type );