- blend_m3_m3m3 and blend_m4_m4m4 now support matrices with negative scales.

- python/mathutils api matrix.lerp(other, factor)
- new function mat3_to_rot_size(), like mat4_to_loc_rot_size but with no location.

source/blender/python/generic/mathutils_vector.c

@@ -670,7 +670,7 @@ static PyObject *Vector_Lerp(VectorObject *self, PyObject *args)
 		return NULL;
 
 	if(self->size != vec2->size) {
-		PyErr_SetString(PyExc_AttributeError, "vector.lerp(): expects (2) vector objects of the same size");
+		PyErr_SetString(PyExc_AttributeError, "vector.lerp(): expects both vector objects to have the same size");
 		return NULL;
 	}