swift234

Fold ExtensibleCollectionType into RangeRaplaceableCollectionType

ExtensibleCollectionType's operations can all be represented by the
primitive range replacement operation, so fold it into
RangeReplaceableCollectionType.

In addition, provide default implementations of
RangeReplaceableCollectionType's methods.

- New tests added for combinations of (static, generic) calls and
  (default, custom) implementations.
- Mark free Swift functions as unavailable with a message to direct the
  developer to the protocol methods.
- Mark ExtensibleCollectionType as available with a message added to
  direct the developer to the right protocol.

rdar://problem/18220295

Swift SVN r29857