Miscellaneous fun with notifications, display vars/funcs, and bug fixes

Miscellaneous fun with notifications, display vars/funcs, and bug fixes

The crusade to purge references to display vars/functions from the game
logic has been completed.

* combat.cc: range-vs-accuracy curve now works correctly for player bow
  shots, and a notification is sent for trying to shoot monsters at point
  blank. Also, notify_mon_hit_armour() now actually gets used and an
  uninitialized variable bug has been squashed.
* display-nc.cc: Removed some misconceived comments, made permobj
  colours actually show up on the screen (rather fewer l_grey items
  now), and added compile-time option to log messages to stderr.
* main.cc: call notify_tick() at the end of every tick to make sure pending
  display updates get flushed.
* map.cc: Removed references to display vars and display_update().
* monsters.cc: Removed references to display vars and display_update().
* notify-local-tty.cc, notify.hh: More notifications! Also, fixing some
  updates that should have set display control flags but didn't.
* objects.cc: Removed reference to display var.
* u.cc: Removed references to display vars and display_update().