swift234

IRGen: Hack in calls to block converter funcs.
Add a mangling for 'block converter' functions and for [objc_block] function types. [objc_block] types also need their own HeapTypeInfo representation that uses ObjC retain/release. When we see a BridgeToBlockExpr, feed the function pointer and context from the Swift closure to the external conversion function and hope we get a block back.

Swift SVN r3899