misc/mc: drop needless run-time dependencies on Aspell and Xlib

Yury V. Zaytsev points out that for X11 and Aspell support, header
files <X11/Xlib.h> and <aspell.h> are only needed during the build,
while their corresponding libraries would be loaded dynamically if
available; if not, mc(1) would still work fine, just without those
features. The source code and ldd(1) output confirm his findings:

% cd $WRKDIR/mc-4.8.30 && grep -R -A1 g_module_build_path *
lib/tty/x11conn.c:  x11_module_fname = g_module_build_path (NULL, "X11");
lib/tty/x11conn.c-  x11_module = g_module_open (x11_module_fname, G_MODULE_BIND_LAZY);
--
src/editor/spell.c: spell_module_fname = g_module_build_path (NULL, "libaspell");
src/editor/spell.c- spell_module = g_module_open (spell_module_fname, G_MODULE_BIND_LAZY);

This allows to enable Aspell support by default and drop X11-less
slave port now that both of these dependencies are build-time only
yet still can be completely disabled via options.

PR: 269120