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)