SODD: Another MAD-X module

The new madx command sodd implements the functionalities of the stand-alone program SODD (Second Order Detuning and Distorsion function) written by F. Schmidt. It provides an easy interface to other MAD-X modules by automatically computing the required input parameters from the last TWISS command. The results are not only stored into files as it is done in the stand alone program but also inside internal MAD-X tables for the use in subsequent MAD-X commands. This note describes the coding implementation and documents the use of the command sodd.