swift234

Switch BooleanLiteralConvertible over to an initializer requirement.

Conforming to BooleanLiteralConvertible now requires

  init(booleanLiteral: Bool)

rather than

  static func convertFromBooleanLiteral(value: Bool) -> Self

This posed a problem for NSNumber's conformance to
BooleanLiteralConvertible. A class needs a required initializer to
satisfy an initializer requirement, but one cannot add a required
initializer via an extension. To that end, we hack the Clang importer
to import NSNumber's initWithBool with the name

  init(booleanLiteral:)

and add back the expected init(bool:) initializer in the
overlay. These tricks make NSNumber even harder to subclass, but we
don't really care: it's nearly impossible to do well anyway, and is
generally a Bad Idea.

Part of rdar://problem/18154091.

Swift SVN r21961