curses: remove unnecessary special handling for dark gray

On terminals with at least 16 colors there should be no need for special
handling dark gray.

The curses code uses COLORS < 16, COLORS <= 16, COLORS > 16, or COLORS >= 16
at several places although I'm not sure if they are correct or which could
possibly be off-by-one errors.

But realistically in this case, we only need to distinguish between 8 color
terminals and terminals supporting more than 8 colors as this will mean the
terminal supports at least 256 colors.

win/curses/cursinit.c

@@ -358,6 +358,11 @@ curses_init_nhcolors(void)
 
 
         if (COLORS >= 16) {
+# ifdef USE_DARKGRAY
+            if (iflags.wc2_darkgray) {
+                init_pair(1, COLOR_BLACK + 8, -1);
+            }
+# endif
             init_pair(9, COLOR_WHITE, -1);
             init_pair(10, COLOR_RED + 8, -1);
             init_pair(11, COLOR_GREEN + 8, -1);
@@ -367,18 +372,6 @@ curses_init_nhcolors(void)
             init_pair(15, COLOR_CYAN + 8, -1);
             init_pair(16, COLOR_WHITE + 8, -1);
         }
-
-        if (can_change_color()) {
-# ifdef USE_DARKGRAY
-            if (COLORS > 16) {
-                color_content(CURSES_DARK_GRAY, &orig_darkgray.r,
-                              &orig_darkgray.g, &orig_darkgray.b);
-                init_color(CURSES_DARK_GRAY, 300, 300, 300);
-                /* just override black colorpair entry here */
-                init_pair(1, CURSES_DARK_GRAY, -1);
-            }
-# endif
-        }
     }
 #endif
 }
@@ -857,14 +850,4 @@ curses_display_splash_window(void)
 void
 curses_cleanup(void)
 {
-#ifdef TEXTCOLOR
-    if (has_colors() && can_change_color()) {
-# ifdef USE_DARKGRAY
-        if (COLORS > 16) {
-            init_color(CURSES_DARK_GRAY, orig_darkgray.r,
-                        orig_darkgray.g, orig_darkgray.b);
-        }
-# endif
-    }
-#endif
 }