In embed.fnc, reorder the symbols conditional on HAVE_INTERP_INTERP.

This reordering removes 2 pre-processor directives.
In the PERL_IMPLICIT_SYS section in perl_free(), use fewer CPP directives.

The diff is actually confusing to look at - the code itself makes things a
lot clearer:

#    ifdef NETWARE
        void *host = nw_internal_host;
        PerlMem_free(aTHXx);
        nw_delete_internal_host(host);
#    else
        void *host = w32_internal_host;
        PerlMem_free(aTHXx);
        win32_delete_internal_host(host);
#    endif