deprecated StackLens and StackLensFamily

https://github.com/scala/scala/commit/3cc99d7b4aa43b1#diff-25
https://github.com/scala/scala/blob/v2.11.0-M7/src/library/scala/collection/immutable/Stack.scala#L50
Merge pull request #588 from xuwei-k/deprecated-stack

deprecated StackLens and StackLensFamily