Replace "domain.com" by "example.com"

Motivation:
* "domain.com" points to a commercial website
* the domain name "example.com" ("example.net", "example.org", and "example.edu") was reserved for documentation purposes and examples of the use of domain names and is used in a generic and vendor-neutral manner

Signed-off-by: xchs <github@gmx.net>
Merge pull request #6212 from xchs/change-example-domain
Replace "domain.tld" with "example.com" (see #6212)
Check only active modules when using `last_update` (see #6139)
Do not redirect to protected pages after logout (see #6210)
Do not redirect to protected pages after logout (see #6210)
Merge remote-tracking branch 'upstream/hotfix/3.1.3' into hotfix/3.1.3