":" hints can't be statically saved.

[toddr]

Right now we have to do this:

    if ( $op->label ) {

        # test 29 and 15,16,21. 44,45
        my $label = $op->label;
        my ( $cstring, $cur, $utf8 ) = strlen_flags($label);
        $utf8 = 'SVf_UTF8' if $cstring =~ qr{\\[0-9]};    # help a little utf8, maybe move it to strlen_flags
        init()->sadd(
            "Perl_cop_store_label(aTHX_ &cop_list[%d], %s, %u, %s);",
            $ix, $cstring, $cur, $utf8
        );
    }

And then later in save_hints strip out : hints when we save them

    return 'NULL' if keys %$hash == 1 and exists $hash->{':'};
    delete $hash->{':'};

Ideally we could just save things statically.