Add close_range(3) function

Add close_range(3) function. This uses the fcntl approach suggested to me by Robert Elz to avoid adding a newsystem call like in https://github.com/NetBSD/src/pull/43 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](https://gnats.netbsd.org/59081)