[perl #115066] Fix wrongly nested ‘use’ deparsing

B::Deparse was incorrectly putting ‘use’ statements and BEGIN blocks
inside other ‘use’ statements containing do-blocks, even if they were
originally outside.

Subroutines (except for cloned closures, which we don’t have to worry
about here) have an OUTSIDE pointer, pointing to the outer sub con-
taining the declaration of the sub in question.  So we can check that
to make sure we are putting the sub declaration in the right place.

Not only does this fix the reported case, but it also will allow
sequence numbers in inner subs to be reused by statements in outer
subs, which I may need in a future commit.
Put PL_cop_seqmax++ code in one spot
t/base/rs.t: Suppress warning
Don’t always skip in-memory tests is t/base/rs.t

There is no PerlIO::via::scalar, as far as I can tell.  In-memory han-
dles just use PerlIO::scalar.

The code was added by cd1a9f552.  I’m not sure it was ever cor-
rect.  It was intended to skip tests under -Uuseperlio (see <20080614182005.yxuyk1mntwkog0o0@horde.wizbit.be>), but
skipped them on all builds.  I’m not sure that we even support
-Uuseperlio any more.

In the mean time, 1ab48e3a screwed up the test count.