permit goto at top level of multicalled sub

permit goto at top level of multicalled sub

A multicalled sub is reckoned to be a pseudo block, out of which it is
not permissible to goto.  However, the test for a pseudo block was being
applied too early, preventing not just escape from a multicalled sub but
also a goto at the top level within the sub.  This is a bug similar, but
not identical, to [perl #113938].  Now the test is deferred, permitting
goto at the sub's top level but still forbidding goto out of it.