'quick_farsight' option

Bite the bullet and add a special purpose boolean option to control
game behavior for random clairvoyance.  When objects or monsters are
discovered, it normally issues "you sense your surroundings" and
performs a getpos() operation which allows the player to browse the
map by moving the cursor around and getting 'autodescribe' feedback.
But there have been complaints that once the hero has the Amulet
(which triggers random clairvoyance even though hero isn't flagged
as having that attribute) the message and pause-to-browse become too
intrusive.

This was initially combined with the 'timed clairvoyance' fix because
they both bump EDITLEVEL to invalidate existing save files, but their
details don't interact so I separated them.

dat/opthelp

@@ -43,6 +43,8 @@ perm_invent    keep inventory in a permanent window               [FALSE]
 pickup_thrown  override pickup_types for thrown objects           [TRUE]
 pushweapon     when wielding a new weapon, put your previously    [FALSE]
                wielded weapon into the secondary weapon slot
+quick_farsight usually skip the chance to browse the map when     [FALSE]
+               randomly triggered clairvoyance takes place
 rawio          allow the use of raw I/O                           [FALSE]
 rest_on_space  count the space bar as a rest character            [FALSE]
 safe_pet       prevent you from (knowingly) attacking your pet(s) [TRUE]