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/command.go

@@ -149,7 +149,7 @@ over:
 		}
 		if found != nil {
 			if !g.levitCheck() {
-				g.pickUp(found.Type)
+				g.pickUp(found.Kind.Glyph())
 			}
 		} else {
 			if !g.Options.Terse {
@@ -409,7 +409,7 @@ func (g *RogueGame) wizardCommand(ch byte) {
 	case CTRL('X'):
 		g.turnSee(p.On(SenseMonsters))
 	case CTRL('~'):
-		if item := g.getItem("charge", int(Stick)); item != nil {
+		if item := g.getItem("charge", KindWand); item != nil {
 			item.SetCharges(10000)
 		}
 	case CTRL('I'):
@@ -425,8 +425,8 @@ func (g *RogueGame) wizardCommand(ch byte) {
 		p.CurWeapon = obj
 		// And his suit of armor
 		obj = newObject()
-		obj.Type = Armor
-		obj.Which = ArmorPlateMail
+		obj.Kind = KindArmor
+		obj.Which = int(ArmorPlateMail)
 		obj.Arm = -5
 		obj.Flags.Set(Known)
 		obj.Count = 1
@@ -671,7 +671,7 @@ func (g *RogueGame) levitCheck() bool {
 // call allows a user to call a potion, scroll, or ring something
 // (command.c call).
 func (g *RogueGame) call() {
-	obj := g.getItem("call", Callable)
+	obj := g.getItem("call", KindCallable)
 	// Make certain that it is something that we want to name
 	if obj == nil {
 		return
@@ -681,20 +681,20 @@ func (g *RogueGame) call() {
 	var know *bool
 	var guess *string
 	it := &g.Items
-	switch obj.Type {
-	case Ring:
+	switch obj.Kind {
+	case KindRing:
 		op = &it.Rings[obj.Which]
 		elsewise = it.RingStones[obj.Which]
-	case Potion:
+	case KindPotion:
 		op = &it.Potions[obj.Which]
 		elsewise = it.PotColors[obj.Which]
-	case Scroll:
+	case KindScroll:
 		op = &it.Scrolls[obj.Which]
 		elsewise = it.ScrNames[obj.Which]
-	case Stick:
+	case KindWand:
 		op = &it.Sticks[obj.Which]
 		elsewise = it.WandMade[obj.Which]
-	case Food:
+	case KindFood:
 		g.msg("you can't call that anything")
 		return
 	default: