Change menu_headings to accept color and attribute

Instead of just accepting an attribute, it's now possible to
use a color, or both color and attribute, for example:

OPTIONS=menu_headings:inverse
OPTIONS=menu_headings:red
OPTIONS=menu_headings:red&underline

Default is still just inverse.
This lets the player change the menu heading color without
needing to use menu colors for them.

Also makes it so the core uses NO_COLOR instead of 0, for all
the menu lines which don't have any prefedefined color.

Tested for tty, curses, x11, qt, and win32

include/winX.h

@@ -157,6 +157,7 @@ typedef struct x11_mi {
     long pick_count;     /* specific selection count; -1 if none */
     char *str;           /* The text of the item. */
     int attr;            /* Attribute for the line. */
+    int color;           /* Color for the line. */
     boolean selected;    /* Been selected? */
     boolean preselected; /*   in advance?  */
     unsigned itemflags;  /* MENU_ITEMFLAGS_foo */