Give item categories and subtypes real types (refactor step 2)

ObjectKind separates what an item is from how it draws: Object.Type
(a byte that doubled as the map character) becomes Kind ObjectKind,
with Glyph() producing the display character and objectKindForGlyph
converting back at the map boundary. KindWand covers the C 'stick'
category. The magic-missile bolt uses KindGold, matching C's literal
o_type='*' trick, with a comment.

PotionKind, ScrollKind, RingKind, WandKind, WeaponKind, ArmorKind and
TrapKind are now iota enums with Stringer (names come from the base
info tables); Object gains typed accessors (obj.RingKind(), ...) and
Launch is typed WeaponKind. beTrapped returns TrapKind. The
getItem/inventory/whatis prompt filters take ObjectKind, with
KindCallable/KindRingOrStick replacing the C CALLABLE/R_OR_S
sentinels; wizard.c's type_name table is subsumed by
ObjectKind.String(). IsRing/IsWearing/initWeapon/doPot signatures are
typed accordingly.

The save format version becomes 5.4.4-go2: the gob field rename would
otherwise silently zero Kind when reading old saves.

No behavior change; full suite green.

game/chase.go

@@ -233,7 +233,7 @@ func (g *RogueGame) chase(tp *Monster, ee Coord) bool {
 								break
 							}
 						}
-						if found != nil && found.Which == ScrollScareMonster {
+						if found != nil && found.ScrollKind() == ScrollScareMonster {
 							continue
 						}
 					}
@@ -375,7 +375,7 @@ func (g *RogueGame) findDest(tp *Monster) *Coord {
 		return &g.Player.Pos
 	}
 	for _, obj := range g.Level.Objects {
-		if obj.Type == Scroll && obj.Which == ScrollScareMonster {
+		if obj.Kind == KindScroll && obj.ScrollKind() == ScrollScareMonster {
 			continue
 		}
 		if g.roomin(obj.Pos) == tp.Room && g.rnd(100) < prob {