Collect slackware

[pombredanne]

See http://www.slackware.com/security/

[armijnhemel]

Instead of scraping it might also be worth looking into subscribing to the mailing list instead and parse the e-mails that are coming in.

[armijnhemel]

The Slackware SSA report numbering seems to be as follows:

SSA:yyyy-dayofyear-sequence

so for example:

SSA:2022-351-01 is the first report sent on the 351st day of 2022

[armijnhemel]

Also see #1172