Remove outdated comment
Inliner: make result value more informative

Instead of just saying whether there was at most one occurrence, return
0, 1 or more. This will be needed to fix a work-duplication inliner bug,
noted in this commit with an XXX comment.
Fix work-duplication inliner bug, thanks to previous commit

Note that this might change the results of the evaluation - please re-run.
Remove outdated comments

These comments are about the Scalac bug fixed by
https://github.com/scala/scala/pull/801.
Disable broken test

This was broken consciously, so it can be disabled.
Switch to latest SBT
Minimal test fix

Silencing a warning for a non-exhaustive match is not a good idea in a
test which should produce a MatchError.
Share and expose a SubquerySharing instance
Fix test failure
Change fix for test failure to silence a warning