- correctly set the return value for the copyin/out fault buffer to 1

- correctly set the return value for the copyin/out fault buffer to 1
  so setfault would return correctly when a page fault was invalid
  (e.g. a syscall with a bad parameter).

  This caused an endless DSI loop, seen when running sendmail which
  does a setlogin() call with a NULL pointer.

- introduce KTR_SYSC tracing. expose the syscallnames[] array to
  make the tracing more readable.