Extended Version of tango.core.Array.distinct

new function distinctSort

(second version fixes some typos)

part was commented out :o

a few thoughts:

• shouldn't distinctSort_ be private?
• why return size_t instead of a slice? (isn't that the way D encourages?)
• isn't there such a function in Tango already? (haven't really had a look yet)

This is almost a direct copy of the existing distinct function. The only thing I changed is that it sorts the sub-groups using a provided function.

Almost every function in core.Array returns a size_t.

What I remember from the discussion on between you and kirs on #d.tango is that this function probably doesn't have enough demand to be included. - Remarks?

why size_t as the return type should be well documented I think.

As for including the function, at least _some_ demand is needed, in the form of sensible usecases.

Or a note as to why this version is better if a replacement is of interest.