Severity: wishlist

As a followup from [1], here is a patchset which replaces the master's
current rejection of confusable quotes on `read', and instead adds a
hint to the error message when evaluating an expression with a
confusable quote leads to an error.

And also highlight such quotes with warning-face.

[1]: https://lists.gnu.org/archive/html/emacs-devel/2018-02/msg00093.html