#153 Change prefix on datafile.

[Todd A. Green]

Need the ability to change the prefix on the datafile
so it can be different from the program used to
generate it (awstats) and the script used to view it
(index.cgi) or whatever.

Currently it's hardcoded to $PROG so it changes
depending on the name of the script. It would be nice
to have it as a config option.