Properly scope `catch` identifier when --screw-ie8

Fix mishoo#344

Better fix for mishoo#343

We can in fact lift sequences, but only if the operation is assignment and
the left-hand side has no side effects nor property access -- that should
guarantee that whatever we place before it cannot affect the sense of the
assignment.

Dropped contrived test case (too hard to support it now), added a more
meaningful one.

Revert #3a81f60 for now

(with it some tests break and it can generate invalid output, see issue mishoo#44)