Add several new features, reorder some code, and continue with the

Add several new features, reorder some code, and continue with the
process of making the script more cross platform friendly.

* Add -i option to automatically install files that do not exist
  on the system already.
* Add the ability to specify DESTDIR.
* Allow the user to specify scripts to run right before the
  comparison starts, and when mm is done. This will
  allow the user to specify customized local behavior, and
  implement features such as automatically deleting files.
* Document the above changes in the man page.
* Switch to using 'ident' for the CVS Id comparison, which
  should help with portability, and makes it faster.
* Reorder, and in one case fix some code by doing things in
  ways that make more sense.
* Check to see if the file exists on the system before doing
  the comparisons. This saves CPU cycles, and streamlines
  the auto-install process.

I used bits and pieces of suggestions and patches from various
people, ultimately too numerous to name. Which is not to say
that they were not both appreciated, and helpful in achieving
the ultimate result.