fix uninitialized variables in container layout

variables `x` and `y` shadowed the parameters, and `containerX`, `containerY`,
`containerWidth` and `containerHeight` were used without being initialized.
they could be replaced by the parameters `width` and `height`

layout/container.lua

@@ -53,20 +53,19 @@ end
 
 function container:draw(x, y, width, height, children, hpad, vpad, alignX)
 	local w, h = children[1]:getSize()
-	local x, y 
 
 	if self.halign == 'stretch' then
 		w = width
 		x = x
 	else
-		x = alignHandlerX(self.halign, containerX, containerWidth, w)
+		x = alignHandlerX(self.halign, x, width, w)
 	end
 
 	if self.valign == 'stretch' then
-		h = h
+		h = height
 		y = y
 	else
-		y = alignHandlerY(self.valign, containerY, containerHeight, h)
+		y = alignHandlerY(self.valign, y, height, h)
 	end
 
 	children[1]:draw(x, y, w, h)