FvwmPager: Use ULONG_MAX to identify a non configured Pixel.

The black pixel is 0, so if a user configures the window foreground
or focus foreground to be black, when testing if the pixel has been
configured, the test fails and the pager falls back to using the
pixel provided by fvwm. Instead use ULONG_MAX to identify if the
window foreground and focus foreground pixel has been defined by
the user or not.

This fixes #1105.

modules/FvwmPager/init_pager.c

@@ -183,9 +183,9 @@ void initialize_desks_and_monitors(void)
 	default_style->bg = GetSimpleColor("white");
 	default_style->hi_fg = GetSimpleColor("black");
 	default_style->hi_bg = GetSimpleColor("grey");
-	default_style->win_fg = None; /* Use fvwm pixel unless defined. */
+	default_style->win_fg = ULONG_MAX; /* Use fvwm pixel unless defined. */
 	default_style->win_bg = None;
-	default_style->focus_fg = None;
+	default_style->focus_fg = ULONG_MAX;
 	default_style->focus_bg = None;
 	default_style->balloon_fg = None;
 	default_style->balloon_bg = None;

modules/FvwmPager/x_pager.c

@@ -2055,7 +2055,7 @@ void setup_balloon_window(PagerWindow *t)
 	Balloon.cs = style->balloon_cs;
 
 	fg = (style->balloon_fg) ? style->balloon_fg :
-	     (style->win_fg) ? style->win_fg : t->text;
+	     (style->win_fg < ULONG_MAX) ? style->win_fg : t->text;
 	XSetForeground(dpy, Balloon.gc, fg);
 
 	XUnmapWindow(dpy, Scr.balloon_w);

modules/FvwmPager/x_update.c

@@ -294,10 +294,10 @@ void do_label_window(PagerWindow *t, Window w, rectangle r)
 	DeskStyle *style = FindDeskStyle(t->desk);
 
 	if (t == FocusWin) {
-		pix = (style->focus_fg) ? style->focus_fg : Scr.focus_win_fg;
+		pix = (style->focus_fg < ULONG_MAX) ? style->focus_fg : Scr.focus_win_fg;
 		cs = style->focus_cs;
 	} else {
-		pix = (style->win_fg) ? style->win_fg : t->text;
+		pix = (style->win_fg < ULONG_MAX) ? style->win_fg : t->text;
 		cs = style->win_cs;
 	}
 	XSetForeground(dpy, Scr.NormalGC, pix);
@@ -453,7 +453,7 @@ void do_border_window(PagerWindow *t, Window w, rectangle r)
 	}
 
 	if (t == FocusWin) {
-		if (style->focus_fg)
+		if (style->focus_fg < ULONG_MAX)
 			XSetForeground(dpy,
 				style->focus_hi_gc, style->focus_fg);
 		else
@@ -464,7 +464,7 @@ void do_border_window(PagerWindow *t, Window w, rectangle r)
 				style->focus_hi_gc, style->focus_hi_gc,
 				WindowBorderWidth);
 	} else {
-		if (style->win_fg)
+		if (style->win_fg < ULONG_MAX)
 			XSetForeground(dpy,
 				style->win_hi_gc, style->win_fg);
 		else