Unix: command line --windowtype:foo fix

initoptions(), including initoptions_finish(), was running to
completion with the default window system before windowtype from the
command was parsed and activated.  When the default window system
is tty without MS-DOS the map type gets set to ascii; command line
--windowtype:X11 doesn't switch it back to the X11 default of tiled.

So,
| NETHACKOPTIONS=windowtype:X11 nethack
ran nethack in tiles mode but
| nethack --windowtype:X11
ran it in text mode (assuming .nethackrc left tiles vs text with the
default setting).

I think this fix is quite iffy but it seems to work as intended....
It reclassifies '--windowtype' as an "early option" in unixmain.c,
and the options.c code ultimately processes it twice.

include/decl.h

@@ -1087,6 +1087,7 @@ struct instance_globals {
     boolean opt_from_file;
     boolean opt_need_redraw; /* for doset() */
     boolean opt_need_glyph_reset;
+    char *cmdline_windowsys; /* set in unixmain.c */
     /* use menucolors to show colors in the pick-a-color menu */
     boolean save_menucolors; /* copy of iflags.use_menu_colors */
     struct menucoloring *save_colorings; /* copy of g.menu_colorings */