Move to a queue-based system call tracing, stop using systrace buffer

Now, we allocate a trace record in the system call and, when we exit, write it
to a queue for the kptrace qid.

Read reads from the queue.

Records are text, delimited by a newline.

The system calls no longer include the systrace_record as a parameter,
it's in the kthread.

This works. It's possible to deadlock by leaving tracing on
and ls -l /prof.

Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>