making curly apostrophe part of a word

[Eric Abrahamsen <eric@ericabrahamsen.net>]

In certain modes (actually just certain files) I'd like the `’'
character to be treated the same as a `'' character with respect to word
movement: ie I'd like M-f to skip over the entirety of both "don't" and
"don’t". I'm editing externally-created files, and don't have the
liberty of changing this.

I thought this would do it:

(modify-syntax-entry ?’ "w")

To give the quote character word syntax, but word-level commands still
treat it as a word boundary. Looking at describe-syntax, it appears to
have the same status as regular old `'' (apart from the "p" flag, which
I don't think is relevant). What am I doing wrong?

Thanks!
E