Fix autocomplete filter function for no \w chars.
In the ovrriden methos filter, regexp check char of term with \b.
This results all no \w chars to omitted, since \b work just with \w.
(this is new aaproche of this commit: https://gerrit.wikimedia.org/r/#/c/mediawiki/extensions/PageForms/+/512528/, modified by suggestion from Thiemo Kreuz)
Change-Id: Ife75c878c28dc3d73a296f5a1c73801a5ef883ce