splitter semantics

[bearophile]

monarch_dodra:

> 1. " hello  ".split() => ["hello"]; //std.string
> 2. " hello  ".splitter() => ["", "hello"];         //std.string
> 3. " hello  ".splitter!isWhite() => ["", "hello"]; //std.algo
> 4. " hello  ".splitter(' ') => ["", "hello", "", ""]; //std.algo

There is a bug report on this stuff (8013). Please model them on 
the ouput of std.string where possible.

Bye,
bearophile