Enforce stricter output escaping for buffer values
BREAKING Rename NotFilter.addfilter to NotFilter.setFilter
BREAKING Rewrite filter parser to be more strict about input.
This significantly changes the sort of filters which the parser files
acceptable. While the old parser would tolerate unescaped characters in
the ()\* set, the new parser requires them to be escaped via the \XX
hex notation. This is in keeping with
RFC 4514
Perform better escaping for values which are not UTF-8