swift234

@objc should be enough to make a protocol a class protocol.

There are very few times where we'd want to use @class_protocol outside of
@objc, and it feels weird to tell someone coming from Objective-C that they
need to mark their already-@objc protocol as @class_protocol. Instead, just
change ProtocolDecl::requiresClass to check for @objc.

(The commit checks for /both/ @objc-the-attribute and the IsObjC flag.
This is to give the right answer before type-checking, or at least the
likely-intended answer.)

<rdar://problem/16302887>

Swift SVN r15060