The line wrapper's `is_word_char` function included the ASCII apostrophe
(U+0027) but not the typographic right single quotation mark `'`
(U+2019) or left single quotation mark `'` (U+2018). When Markdown
rendering produces curly quotes, words like `won't` were being split at
the apostrophe during line wrapping, producing `won` at the end of one
line and `'t` at the start of the next.

This adds both typographic quote characters to `is_word_char` so they
are treated the same as the ASCII apostrophe.

Release Notes:

- Fixed line wrapping splitting words at typographic apostrophes (e.g.
"won't" breaking as "won" / "'t").