create recipients database for Erwin Hoffmans RECIPIENTS extension

[Frank Tegtmeyer <fte-sub-qmail@fte.to>]

Erwin Hoffmann <feh@fehcom.de> writes:

> There are scripts available to transform local and virtual user to the
> recipients format, which is fastforward compatible.

I tried some of the scripts and wasn't satisified at all. The provided
Python script was a good starting point to hack something better.

The result is here:
http://fte.tegtmeyer.net/djbware/create_recipients.py

Changes from the original script:
- minimize memory usage
- handles all virtual setups (vmail should work too, please check)
- tries to imitate qmail delivery as close as possible
- reduces large alias lists if there is a "base" alias (Erwins
  patch allows all extensions to a base address)

Address sources:
- relay domains (generated as wildcards)
- local and virtual domains
- users/assign
- local users
- alias user
- .qmail files for users, alias and virtual domains
- vpopmail password files

The output still may contain duplicates which have to be sorted out by
"sort -u". This was the tradeoff for low memory impact.

Regards, Frank