swift234

Don't require 'Self.' within the where clause of a constrained extension.

Within the where clause of a constrained (protocol) extension, allow
us to find associated types of that protocol and anything it inherits
via unqualified lookup, e.g.,

  extension SequenceType where Generator.Element : Equatable { }

rather than

  extension SequenceType where Self.Generator.Element : Equatable { }

Implements rdar://problem/20722467.

Swift SVN r28208