Create vertical_menu widget

This commit implements a vertical menu widget, which should be quite a bit more flexible than
what we currently have.

It defines interfaces in order to respond to selection changes, show and hide. And has a i_item_widget
interface class to allow you to use custom item widgets.

This is done in preparation for adding a debug menu, in which I kinda want to add toggle options
while using the same vertical_menu widget.

Right now, vertical_menu is only used in Select_Menu. Needless to say that Select_Menu was reworked quite a bit.
Still, in terms of visuals or functionality, the changes should be invisible for now. I mean, I didn't do anything *new* with it yet.

source/script_array.cpp

@@ -682,6 +682,8 @@ const script_obj_params event_script_params[SCRIPT_SIZE] = {
 
 void populate_lang_menu()
 {
+    langs.clear_options();
+
     langs.add_option(GENERAL_option_english, ENG_ID);
     langs.add_option(GENERAL_option_japanese, JPN_ID);
     langs.add_option(GENERAL_option_spanish, SPA_ID);
@@ -696,6 +698,8 @@ void populate_lang_menu()
 
 void populate_game_menu(int lang)
 {
+    games.clear_options();
+
     switch (lang)
     {
     case (JPN_ID):
@@ -856,7 +860,6 @@ bool run_conditional(int index)
         games.set_lang(static_cast<u8>(lang));
         party_data.set_lang(static_cast<u8>(lang));
         return true;
-
     case CMD_GAME_MENU:
         populate_game_menu(party_data.get_lang());
         game = games.select_menu_main();
@@ -866,7 +869,6 @@ bool run_conditional(int index)
         }
         party_data.set_game(game);
         return true;
-
     case CMD_SLIDE_PROF_LEFT:
         for (int i = 0; i <= (8 * 7); i += 2)
         {