public string tokenize_and_fold (string transit_locale, out string ascii_alternates)
string and performs folding on each token.
A token is a non-empty sequence of alphanumeric characters in the source string, separated by non-alphanumeric characters. An "alphanumeric" character for this purpose is one that matches isalnum or ismark.
Each token is then (Unicode) normalised and case-folded. If
ascii_alternates is non-null and
some of the returned tokens contain non-ASCII characters, ASCII alternatives will be generated.
The number of ASCII alternatives that are generated and the method for doing so is unspecified, but
translit_locale (if specified)
may improve the transliteration if the language of the source string is known.
a return location for ASCII alternates
the language code (like 'de' or 'en_GB') from which
the folded tokens