more menu header tweaking re options

<color>
off: map, menu items, menu headings, menu prompt/title all, everything should have color suppressed.

<curses guicolor>
on: map, menu items, menu headings, menu prompt/title can all feature color, as can
menu borders, menu-selector letters.
off: map, menu headings, menu prompt and menu items (menucolors on) can still feature color,
but all other non-map features such as menu borders, menu-selector
letters will not have color.

<menucolors>
on: menu items can have colors if they match one of the regex in config
file; menu headings, menu prompt can also be in color (based on menu_headings option).
off: menu items won't have colors, but menu headings, menu prompt still
will feature colors (based on menu_headings option); those are not impacted by turning
off menucolors.

src/decl.c

@@ -628,6 +628,7 @@ const struct instance_globals_o g_init_o = {
     FALSE, /* opt_from_file */
     FALSE, /* opt_need_redraw */
     FALSE, /* opt_need_glyph_reset */
+    FALSE, /* opt_need_promptstyle */
     /* pickup.c */
     0,  /* oldcap */
     /* restore.c */