swift234

Don't apply module-shadowing rules to protocol members.

It's common for a requirement in a protocol and an implementation of that
requirement in a protocol extension to have the same
signature. Overload resolution prefers the requirement (which
dispatches dynamically), but that was being subverted by the shadowing
rules when the protocol came from an imported module and the extension
was in the current module. Fixes rdar://problem/21739333.

Swift SVN r30598