swift234

[stdlib] Add support for bound protocols

Protocols with associated types can't currently be used as existential
types.  Combined with the inability to create type constraints on
generic functions nested in generic types based on the outer type and
the inability to create closures of generic type and the inability to
create protocol constraints that require generic functions and the
inability to create protocols with init() requirements... and this is
what we get.

Swift SVN r10034