exit codes in docs [was: Correction to integrating-with-postfix]

[Clint Adams]

> How about adding another switch to bogofilter that makes it return an
> exit code that's equal to its spamicity value?  IE a 1.00 count would
> return a 100, a non-spam of 0.04 would return a 4.

It boggles my mind that people are using exit codes at all for what is
clearly program output.