vt: Improve multi lingual word separation.

Suggested by: Tomoaki AOKI <junchoon@dec.sakura.ne.jp>
Differential Revision: https://reviews.freebsd.org/D35552
PR: 263084
Sponsored by: NVIDIA Networking

(cherry picked from commit 9971e6aff1bef3d456172c41a3df3ce7266517cf)