NSString example

Same as @cvasilak I noticed with Swift beta5 it looks like extension methods IMPL can not be set. Custom class methods can not be set either.

Even though MyClass inherits from NSObject (which is a pre-requisites for swizzling), testClassMethod is not replaced by swizzled_testClassMethod

However defaultCStringEncoding is replaced by swizzled_defaultCStringEncoding

Those examples used to work on beta4, not sure what's happening in beta5. Broken compatibility with objc?
Help welcome.