bug#44974: dabbrev-expand doesn't know wide commas are commas yet

[積丹尼 Dan Jacobson]

The command dabbrev-expand is bound to M-/.

It is great, except it needs to be updated, to know that
"，" is a comma, just like ",".

哇，哈<ESC />
a,bb<ESC />

Scanning for dabbrevs...done
user-error: No dynamic expansion for ‘哇，哈’ found
Scanning for dabbrevs...done
user-error: No dynamic expansion for ‘bb’ found

Note how the latter doesn't have the "a," glued to it.

That means it is operating correctly. The former needs to be updated to
act like the latter.

P.S., I didn't test any other wide punctuation, e.g.. "。", etc.

emacs-version "27.1"