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/Qt4/qt4bind.cpp

@@ -730,6 +730,7 @@ struct window_procs Qt_procs = {
     | WC_FONT_MAP | WC_TILE_FILE | WC_TILE_WIDTH | WC_TILE_HEIGHT
     | WC_PLAYER_SELECTION | WC_SPLASH_SCREEN,
     0L,
+    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},   /* color availability */
     nethack_qt4::NetHackQtBind::qt_init_nhwindows,
     nethack_qt4::NetHackQtBind::qt_player_selection,
     nethack_qt4::NetHackQtBind::qt_askname,