swift234

[PrintAsObjC] Print argument names for function/block types

Including the argument names helps code completion in Xcode.

Fixes SR-365.

Also fixes an issue where a property of a block/function type whose name
is a clang keyword would produce an invalid declaration, e.g.

    var `struct`: (Int -> Int)?

was printing as

    @property (nonatomic, copy, getter=struct, setter=setStruct:) NSInteger (^ _Nullable struct)(NSInteger)_;