Avoid extraneous ‘();’ when deparsing just subs

34b54951 caused a program that is empty apart from sub definitions to
be deparsed with ‘();’ for the main sub.  Previously it was omitted.
This commit removes it, not only for the sake of backward-compatibil-
ity, but also because ‘();’ is not a particularly sane way of dumping
an empty program.
Deparse formats in the right spot

Formats need the same logic applied in 34b54951568, to avoid this:

Input:

{
    my $x;
    format STDOUT =
@
$x
.
}
__END__

$ pbpaste|./perl -Ilib -MO=Deparse
{
    my $x;
}
format STDOUT =
@
$x
.
__DATA__
- syntax OK

That $x in the format is now global, not lexical.

Also, we need to make sure the sequence numbers are correct.  The
statement after the format stopped having a higher sequence number
than CvOUTSIDE_SEQ(format) in 8635e3c238f, because the ‘pending’
sequence number set aside for the nextstate op created just after com-
pile-time block exit (which nextstate op comes before the block) was
not actually being used by newFORM (unlike newATTRSUB), so the follow-
ing statement was using that number.
Remove comp/form_scope.t from deparse-skips.txt

It passes!
deparse-skips.txt: Note some skip reasons
Remove comp/hints.t from deparse-skips.txt

It passes, probably due to BEGIN block fixes.
Remove comp/opsubs.t from deparse-skips.txt

It passes.  Since when I don’t know.