kien/ctrlp.vim — pull request #197 by mattn (2012-05-08 07:36:50+00:00)
Title: use 0x27. doc file must be encoded with latin-1.

It seems that doc contains 0x2019 instead of single quote. Vim show helpfile as utf-8 or latin-1. So if I uses vim with non-utf-8 and non-latin-1 encoding, 0x2019 breaks texts.
In the world, there are many users who uses vim with non-utf-8 encodings but multibyte encodings.
I'm guessing you've better to use 0x27 instead of 0x2019.