Sorted collections

[alexeyshockov]

Optimizations and interface for sorted collections.

Interface:

• sorted set builder,
• sorted collection builder,
• sorted map builder.

Thoughts on implementation: collect (as is), sort in build().

Optimizations:

• binary search (Collection::contains(), Map::containsKey()).

[alexeyshockov]

Binary search cannot be implemented on abstract iterator. Implemented only available on some indexed storage, i.e. only after creating (with builder) or freezing (with __clone()), when SplFixedArray available.

Low priority.