Add close_range() system call

[ricardobranco777]

Adapt existing code in compat_linux for close_range and make it use the new native system call.

The existing test code for closefrom(3) was adapted and extended for close_range(2).

The manpage was adapted from FreeBSD using the Linux names for the parameters:
https://man.freebsd.org/cgi/man.cgi?query=close_range&sektion=2&n=1

Fixes kern/59081

CLOSE_RANGE_UNSHARE was removed as it doesn't make sense on NetBSD which lacks unshare(2). From the Linux documentation:

       CLOSE_RANGE_UNSHARE is conceptually equivalent to
           unshare(CLONE_FILES);
           close_range(first, last, 0);

[zoulasc]

I think UNSHARE was implemented before and it was the same way sharing is done and undone in the clone system call. I added it back. I patched, I am doing a build now and will fix the sets.