Version 1.50

- Split the match extraction via pattern match from the window / buffer iteration, which now takes a generic Funcref, allowing for other algorithms: Remove ...Matches... from the s:FindMatchesIn...() functions. Extract s:MatchInCurrent() and s:MatchInBuffer(). Add CompleteHelper#Find() generic alternative to CompleteHelper#FindMatches() that takes a Funcref instead of a regular expression.
- Expose CompleteHelper#AddMatch().
- ENH: Add a:options.abbreviate and evaluate in CompleteHelper#AddMatch(). This saves completion plugins from doing an additional map() over the List of matches.