Rename item-subsystem methods (refactor step 5, items)

getItem→promptPackItem now returns (obj, ok) instead of a nil-signaling
pointer; invName→inventoryName; doPot→applyPotionFuse. C breadcrumbs
kept. Behavior unchanged; suite green.

game/armor.go

@@ -6,8 +6,8 @@ package game
 func (g *RogueGame) wear() {
 	p := &g.Player
 
-	obj := g.getItem("wear", KindArmor)
-	if obj == nil {
+	obj, ok := g.promptPackItem("wear", KindArmor)
+	if !ok {
 		return
 	}
 
@@ -32,7 +32,7 @@ func (g *RogueGame) wear() {
 
 	g.wasteTime()
 	obj.Flags.Set(Known)
-	sp := g.invName(obj, true)
+	sp := g.inventoryName(obj, true)
 	p.CurArmor = obj
 
 	if !g.Options.Terse {
@@ -70,7 +70,7 @@ func (g *RogueGame) takeOff() {
 		g.addmsgf("you used to be")
 	}
 
-	g.msg(" wearing %c) %s", obj.PackCh, g.invName(obj, true))
+	g.msg(" wearing %c) %s", obj.PackCh, g.inventoryName(obj, true))
 }
 
 // wasteTime does nothing but let other things happen (armor.c waste_time).