linux: Add system calls required by Node.js

This wires various system calls that are required by Node.js to the
syscall() libc function.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: David Halls <dahalls@gmail.com>
[ penberg: fold multiple patches into one ]
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>