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/command.go

@@ -453,7 +453,7 @@ func (g *RogueGame) wizardCommand(ch byte) {
 	case CTRL('X'):
 		g.turnSee(p.On(SenseMonsters))
 	case CTRL('~'):
-		if item := g.getItem("charge", KindWand); item != nil {
+		if item, ok := g.promptPackItem("charge", KindWand); ok {
 			item.Charges = 10000
 		}
 	case CTRL('I'):
@@ -738,9 +738,9 @@ 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", KindCallable)
+	obj, ok := g.promptPackItem("call", KindCallable)
 	// Make certain that it is something that we want to name
-	if obj == nil {
+	if !ok {
 		return
 	}
 
@@ -820,7 +820,7 @@ func (g *RogueGame) current(cur *Object, how, where string) {
 		}
 
 		g.InvDescribe = false
-		g.addmsgf("%c) %s", cur.PackCh, g.invName(cur, true))
+		g.addmsgf("%c) %s", cur.PackCh, g.inventoryName(cur, true))
 
 		g.InvDescribe = true
 		if where != "" {