Fixed a broken link to FastCgiExternalServer directive documentation

[javiereguiluz]

This fixes #7080.

---

The previous official website (fastcgi.com) is down and I can't find this doc on the official Apache website. This is the only link that I found.

[xabbuh]

What about linking https://wiki.apache.org/httpd/HelpOnInstalling/FastCgi#FastCgiExternalServer instead?

[javiereguiluz]

@xabbuh is that wiki reliable? It doesn't look like an official doc. Besides, it only explains 2 config options, and the Oracle doc explains 6 options and seems to explain things better.

[wouterj]

What about http://htmlpreview.github.io/?https://github.com/FastCGI-Archives/mod_fastcgi/blob/master/docs/mod_fastcgi.html#FastCgiExternalServer ? This seems to be the official archive of the page we linked to.

[javiereguiluz]

@wouterj the http://htmlpreview.github.io website doesn't look very reliable to me and it doesn't look official. I'd go for the URL proposed by Christian or the one Oracle.com one.

[xabbuh]

Then let's go with the Oracle one.

[javiereguiluz]

Rebased to fix conflicts.

[javiereguiluz]

Closing it in favor of #7791.