Syntax: list or range of characters, as inside REX []
The Language Characters setting controls what characters
constitute a language query. Query terms composed entirely of these
characters are considered language terms, and have Word Forms
processing applied. The syntax is a list of characters (no
separation), and/or a range of characters; the same as a REX character
class (without the brackets). The default is
\alpha\'\x80-\xFF
, ie. alphabetic, hi-bit (for UTF-8) and
apostrophe (for contractions). For best results, all characters that
could match part of a Word Definition expression
(here) should usually also be listed in
Language Characters.