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.

src/decl.c

@@ -528,6 +528,7 @@ const struct instance_globals g_init = {
     FALSE, /* opt_from_file */
     FALSE, /* opt_need_redraw */
     FALSE, /* opt_need_glyph_reset */
+    NULL, /* cmdline_windowsys */
     FALSE, /* save_menucolors */
     (struct menucoloring *) 0, /* save_colorings */
     (struct menucoloring *) 0, /* color_colorings */