Revert "Merge pull request #10397 from BMorearty/remove-varargs-from-in-4-0-stable"

This reverts commit a8ef0bbb776b734b80853dfb3c7553d334cb9fe8, reversing
changes made to 1296adb90b3ffd478d988186bc82a96757b219db.

Reason: Partially revert this commit and properly deprecate #in? with
multiple arguments in 4-0.