This is done for comparing old with new

Add the path cases without changing the whole logic

If we refer to a path `a.b`, we should mark `a.b` as used,
which is better than marking `a`.

Needed to make stdlib2-cc go through.

There were two errors. One in LayListIterable required a type annotation
and a tweak to markFree. The other in Vieew.scala required a cast, but this could be fixed
with better handling of pattern matching. path-patmat-should-be-pos.scala is a minimization.

x*? is x.type @reach @maybe. This was not recognized before.

We extend the grammar to allow e.g. `Iterator[T]^ @use`.

Convert remaining occurrences in tests to @use

The new encoding wraps such capabilities with @use instead of relying on a
@ReachUnderUse annotation. Advantage: This can generalize to capture set variables
under @use.