Replace HTTP links with HTTPS ones: 9P FILE SYSTEM

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
If not .svg:
For each line:
If doesn't contain `\bxmlns\b`:
For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
If both the HTTP and HTTPS versions
return 200 OK and serve the same content:
Replace HTTP with HTTPS.

Signed-off-by: Alexander A. Klimov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/filesystems/9p.rst

···
 The best detailed explanation of the Linux implementation and applications of
 the 9p client is available in the form of a USENIX paper:
 
-   http://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html
+   https://www.usenix.org/events/usenix05/tech/freenix/hensbergen.html
 
 Other applications are described in the following papers: