default options for diff. These options are interpreted first and can be
overwritten by explicit command line parameters.
* Add the "-o" option to specify old-traditional output style.
* Add utility functions for env vars obtained from GNU Grep 2.3h.
Subject: man pages for diff et al.
I finally got tired of not having man pages for diff and friends, so I
edited the appropriate sections of the texinfo manual into man format.
