Updated with latest code.

Updated with latest code.
* runtime/transport/ring_buffer.c (_stp_ring_buffer_disable_cpu): New
  function.
  (_stp_ring_buffer_enable_cpu): Ditto.
  (_stp_ring_buffer_cpu_disabled): Ditto.
  (_stp_ring_buffer_empty_cpu): Only checks online cpus (instead of all
  possible cpus).
  (_stp_find_next_event): Ditto.
  (_stp_ring_buffer_iterator_increment): Calls
  _stp_ring_buffer_disable_cpu()/_stp_ring_buffer_enable_cpu() around
  ring_buffer_* calls.
  (_stp_ring_buffer_consume): Ditto.
  (_stp_peek_next_event): Ditto.
  (_stp_buffer_iter_finish): New function.
  (_stp_buffer_iter_start): Ditto.
  (_stp_data_read_trace): Uses
  _stp_buffer_iter_start()/_stp_buffer_iter_finish().
  (_stp_data_write_reserve): Checks to see if the cpu is disabled (with
  _stp_ring_buffer_cpu_disabled() before reserving memory.  Uses
  _stp_buffer_iter_start()/_stp_buffer_iter_finish().
  (_stp_transport_data_fs_init): Initializes buffer iterators.