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

win/curses/cursinvt.c

@@ -22,6 +22,7 @@ static void curs_show_invt(WINDOW *);
 struct pi_line {
     char *invtxt;  /* class header or inventory item without letter prefix */
     attr_t c_attr; /* attribute for class headers */
+    int color;
     char letter;   /* inventory letter; accelerator if this was really a menu;
                     * used to distinguish item lines from header lines and for
                     * display (no selection possible) */
@@ -290,6 +291,7 @@ curs_add_invt(
     int linenum,      /* line index; 1..n rather than 0..n-1 */
     char accelerator, /* selector letter for items, 0 for class headers */
     attr_t attr,      /* curses attribute for headers, 0 for items */
+    int clr,          /* NetHack color for headers, NO_COLOR for items */
     const char *str)  /* formatted inventory item, without invlet prefix,
                        * or class header text */
 {
@@ -309,6 +311,7 @@ curs_add_invt(
     newelement.invtxt = dupstr(str);
     newelement.c_attr = attr; /* note: caller has already converted 'attr'
                                * from tty-style attribute to curses one */
+    newelement.color = clr;
     newelement.letter = accelerator;
     aptr[pi.inuseindx++] = newelement;
 
@@ -373,7 +376,7 @@ curs_show_invt(WINDOW *win)
         str = pi.array[lineno].invtxt;
         accelerator = pi.array[lineno].letter;
         attr = pi.array[lineno].c_attr;
-        color = NO_COLOR;
+        color = pi.array[lineno].color;
 
         if (accelerator)
             ++item_count;
@@ -413,7 +416,6 @@ curs_show_invt(WINDOW *win)
 
             /* only perform menu coloring on item entries, not subtitles */
             if (iflags.use_menu_color) {
-                attr = 0;
                 get_menu_coloring(str, &color, (int *) &attr);
                 attr = curses_convert_attr(attr);
             }