Support unicode punctuation

[Daniel James]

Spirit 1's punct_p uses the standard C locale ispunct. So use something that supports unicode punctuation.

Maybe also add a way to choose the locale to use and look for anywhere else that the locale matters.

​David Abrahams wrote:

It seems like Quickbook defines "punctuation" as whatever the 'C' locale says it is. As a result, none of the following foo's are italicized:

/foo/—a generic name used in programming—came to being after WWII.

“/foo/” came into being after WWII.

This fact (if I have it right) should be documented.

[QB should be fixed to handle unicode input.]