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/X11/winX.c

@@ -107,6 +107,7 @@ struct window_procs X11_procs = {
     WC2_FLUSH_STATUS | WC2_RESET_STATUS | WC2_HILITE_STATUS |
 #endif
     0L,
+    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},   /* color availability */
     X11_init_nhwindows,
     X11_player_selection, X11_askname, X11_get_nh_event, X11_exit_nhwindows,
     X11_suspend_nhwindows, X11_resume_nhwindows, X11_create_nhwindow,