For reasons unknown, the nfs locking code used a fifo to send requests to

For reasons unknown, the nfs locking code used a fifo to send requests to
userland and a dedicated system call to get replies.

The vnode-bypass of fifos broke this into a panic.

Ditch all the magic and create a device /dev/nfslock instead, and
use that for both directions apart from the shorter path, this is
also faster because the device driver runs Giant free using the
vnode bypass.

Noticed by:	marcel