Code and style cleanup in own modules in BKE and also mball module

- Make sure functions are named in way BKE_<object>_<action> (same way as RNA callbacks)
- Make functions which are used by mball.c only static and remove their prototypes
  from public header file.

Further cleanup is coming.

source/blender/python/mathutils/mathutils_geometry.c

@@ -1011,7 +1011,7 @@ static PyObject *M_Geometry_interpolate_bezier(PyObject *UNUSED(self), PyObject
 
 	coord_array = MEM_callocN(dims * (resolu) * sizeof(float), "interpolate_bezier");
 	for (i = 0; i < dims; i++) {
-		forward_diff_bezier(k1[i], h1[i], h2[i], k2[i], coord_array + i, resolu - 1, sizeof(float) * dims);
+		BKE_curve_forward_diff_bezier(k1[i], h1[i], h2[i], k2[i], coord_array + i, resolu - 1, sizeof(float) * dims);
 	}
 
 	list = PyList_New(resolu);