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/curses/cursmain.c

@@ -51,6 +51,7 @@ struct window_procs curses_procs = {
      | WC2_FLUSH_STATUS | WC2_TERM_SIZE
      | WC2_STATUSLINES | WC2_WINDOWBORDERS | WC2_PETATTR | WC2_GUICOLOR
      | WC2_SUPPRESS_HIST),
+    {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},   /* color availability */
     curses_init_nhwindows,
     curses_player_selection,
     curses_askname,