Single quote path is cached incorrectly

We came across a bug in our cache where someone typed `http://example.com/'` instead of `http://example.com/` for the first hit after a fresh install. That page is (supposed to be) a 404, but for some reason it got cached, and it got cached as `/index.html`. When the user changed from `/'` to `/` they were served the cached page in place of the correct content.

This seems to be special to the single quote character. I tried to repro with double quote, pipe, pre-escaped values, etc. and everything was escaped (e.g. `" => %22`) as expected. Bare question mark was stripped and cached as the base page, as I would expect.

I haven't had a chance to set up a limited test case to repro, and unfortunately I can't share our configuration - but I can try any patch, logging or configuration change that you suggest. I was looking at https://github.com/Automattic/wp-super-cache/commit/617deac2628915761e8928f4d336ed4cffb71ee0 and https://github.com/Automattic/wp-super-cache/commit/4d0f06e119f0b579a9a730bbb16bb9bf35346e1d with the hope that those would be the problem, but unfortunately it does repro for us under 1.4.5.

I did "fix" the problem by adding `"'"` to the `auto_rejected` array in [wp-cache-phase2.php](https://github.com/Automattic/wp-super-cache/blob/master/wp-cache-phase2.php#L141), but A) that's certainly not the correct place to fix this, B) I'm hoping that this is a known problem for something stupid I'm doing in the config, and C) it might be an actual bug that others might encounter.