Return Range.Exclusive on RichInt.until instead of abstract Range

[ausmarton]

Fixes scala/bug#11875

Shuffling an exclusive range of Ints created using until would fail in the block below as a result of the return type being an abstract type: Range, causing the Random.shuffle to look for an implicit of type: scala.collection.BuildFrom[Range, Int, _].

scala.util.Random.shuffle(1 to 10)

In addition, this change would also align the types which extend RangedProxy[T], namely: RichInt and IntegralProxy[T] in terms of their return types for .until. While IntegralProxy[T].until already returned a NumericRange.Exclusive[T], RichInt.until returned an abstract Range.

P.S.: This is my first PR here. Any feedback/suggestions are welcome and would be greatly appreciated. Thanks

[ausmarton]

/rebuild

[som-snytt]

This probably necessarily runs afoul of compatibility constraints:

[error] Saved log of library/mimaReportBinaryIssues:
[error]  * extension static method until$extension(Int,Int,Int)scala.collection.immutable.Range in 
class scala.runtime.RichInt has a different result type in current version, where it is 
scala.collection.immutable.Range#Exclusive rather than scala.collection.immutable.Range

[ausmarton]

Thanks very much. It seems like the fix is going to be a bit more involved considering compatibility constraints.