Ticket #3247: refactoring of status_msg engine.

Initial commit: create global timer.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(mc_time_elapsed): add new function to detect elapsed time intervals.

The author of initial patch is Egmont Koblinger.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
status_msg_t: reimplement delay usage.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Reduce update rate in the "Directory scanning" dialog.

As a result, directory scannig is faster than before.

The author of idea and initial patch is Egmont Koblinger.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
(status_msg_init): repaint screen forced to remove previous finished dialog.

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>
Merge branch '3247_status_msg_update_rate'

* 3247_status_msg_update_rate:
  (status_msg_init): repaint screen forced to remove previous finished dialog.
  Reduce update rate in the "Directory scanning" dialog.
  status_msg_t: reimplement delay usage.
  (mc_time_elapsed): add new function to detect elapsed time intervals.
  Ticket #3247: refactoring of status_msg engine.