Prevent unwanted line breaks in

 tags

By default, Mantis wraps text within 
 tags at 100 chars (see

$g_wrap_in_preformatted_text option).

If the text within the tag contains Unicode extended characters, the

regex performing the wrap does not count them properly, as pcre works on

bytes, causing line breaks to be added in the wrong place.
Adding 'u' modifier to the regex fixes the behavior, as suggested by

cproensa.
Fixes 0021410