[$] System-call wrappers for glibc

The GNU C Library has long had a reputation for being hostile to the
addition of wrappers for new Linux system calls; that has resulted in many
system calls being unsupported by the library for years. That situation is
changing, though. During the Toolchain microconference at the 2019 Linux
Plumbers Conference, Maciej Rozycki talked about glibc's new attitude
toward system-call wrappers, but also served notice that there is still
significant work to do for the addition of any new system call.