lualoader: Use the key that interrupts autoboot as a menu choice

This matches forth behavior. Hitting "6" when autobooting at the welcome
menu will now take you directly to the "Boot Options" menu.

We likely have some slight optimizations we should make, like not checking
autoboot every time we open a new menu and things of this nature. Further
work will go towards this end.

stand/lua/menu.lua

@@ -291,11 +291,13 @@ function menu.run(m)
 	screen.defcursor()
 	local alias_table = drawer.drawscreen(m)
 
-	menu.autoboot()
+	-- Might return nil, that's ok
+	local autoboot_key = menu.autoboot()
 
 	cont = true
 	while cont do
-		local key = io.getchar()
+		local key = autoboot_key or io.getchar()
+		autoboot_key = nil
 
 		-- Special key behaviors
 		if (key == core.KEY_BACKSPACE or key == core.KEY_DELETE) and
@@ -360,13 +362,13 @@ end
 
 function menu.autoboot()
 	if menu.already_autoboot then
-		return
+		return nil
 	end
 	menu.already_autoboot = true
 
 	local ab = loader.getenv("autoboot_delay")
 	if ab ~= nil and ab:lower() == "no" then
-		return
+		return nil
 	elseif tonumber(ab) == -1 then
 		core.boot()
 	end
@@ -395,7 +397,7 @@ function menu.autoboot()
 				print("                                        "
 				    .. "                                        ")
 				screen.defcursor()
-				return
+				return ch
 			end
 		end