Support fcntl() F_SETOWN and F_GETOWN

[JustineTunney]

I'm working on a project called Blinkenlights which is a virtual machine that lets Haiku run x86_64-linux binaries. I'm doing that by polyfilling the Linux SYSCALL ABI onto POSIX APIs.

One of the APIs I need, in order to support programs like Emacs, would be the following fcntl() commands:

• F_SETOWN
• F_GETOWN

I'm reasonably certain that these are mandatory APIs per POSIX.1-2017, since they're not explicitly marked as XSI extensions. See:

• ​https://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html
• ​https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/fcntl.h.html

Thanks!

[waddlesplash]

It appears we do not actually send SIGURG at present. So, that needs to be fixed before (or simultaneously with) this issue.