has_color() performance fixes

Performance profiling showed that multiple strcmpi() calls were
occurring each and every time a character was going to the map.

This update:
- honors the WC_COLOR capability
- It allows a window-port to control individual color availability should the window-port wish to do so.
- Makes checking on the individual colors for the active window-port is a straightforward table lookup at the CLR_ offset.

iflags.use_color remains a master on/off switch for use of color, regardless of the capability
compiled into the game (default TRUE).

The has_color() routine, which is now a shared routine in src/windows.c, could likely be made
into a simple macro to eliminate the function call, but this update does not go that far.

This hits a lot of port files due to the window-port interface change, mostly cookie-cutter.

win/gem/wingem.c

@@ -43,7 +43,9 @@ struct window_procs Gem_procs = {
         | WC_FONT_TEXT | WC_FONT_MAP | WC_FONTSIZ_MESSAGE | WC_FONTSIZ_STATUS
         | WC_FONTSIZ_MENU | WC_FONTSIZ_TEXT | WC_FONTSIZ_MAP | WC_TILE_WIDTH
         | WC_TILE_HEIGHT | WC_TILE_FILE | WC_VARY_MSGCOUNT | WC_ASCII_MAP,
-    0L, Gem_init_nhwindows, Gem_player_selection, Gem_askname,
+    0L,
+    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},   /* color availability */
+    Gem_init_nhwindows, Gem_player_selection, Gem_askname,
     Gem_get_nh_event, Gem_exit_nhwindows, Gem_suspend_nhwindows,
     Gem_resume_nhwindows, Gem_create_nhwindow, Gem_clear_nhwindow,
     Gem_display_nhwindow, Gem_destroy_nhwindow, Gem_curs, Gem_putstr,