use class() in more places

code/ui/prompt.lua

@@ -13,7 +13,7 @@ local function backspace(text)
 	return ""
 end
 
-Prompt = {
+Prompt = class(nil, {
 	-- defaults for instance variables
 	pos = { x = 10, y = 10 },
 	input = "",
@@ -23,7 +23,7 @@ Prompt = {
 	color = {1,1,1,1},
 	background_color = {0,0,0,1},
 	active_prompt = nil,
-}
+})
 function Prompt:cancelActive()
 	if Prompt.active_prompt then
 		Prompt.active_prompt.canceled = true
@@ -33,7 +33,6 @@ end
 function Prompt:new(o)
 	o = o or {}
 	setmetatable(o, self)
-	self.__index = self
 	return o
 end