fsirand(8): Fix security claims.

PR misc/58063

branches: 1.10.16; 1.10.24;
Document author and the version fsirand appeared.
Bump date.

Convert TNF licenses to new 2 clause variant

branches: 1.8.20; 1.8.22;
Remove the SECURITY CONSIDERATIONS section which stated that the
implementation didn't used a good random generator, this is not true
anymore since arc4random(3) is used these days.

Pointed out by Jeff Ito in PR/30321

change -F semantics to treat the argument as a file system image; open it
`as-is' without attempting to determine the device name with opendisk(3),
and don't attempt to read a disklabel.

- add -F - manipulate a file system image in a regular file (instead of
a special device).
- implement statistics printing on SIGINFO

Remove some trailing whitespace.

fix nested extern. While I am here assign copyright to TNF.

Implement a new manual page category ``SECURITY CONSIDERATIONS''
(suggested by mycroft)

* cleanup for WARNS=1
* prefix hex numbers with '0x'

First pass at fsirand. Needs /dev/random to do things right.