Foundation: workaround the frontend trying to keep sugar

The compiler is working hard to keep the type sugar on the interface for
even an internal interface.  The type sugar being preserved causes a
deserialization failure on Darwin.  Use an equivalent local typealias to
avoid the issue.

Author: compnerd

Foundation/Thread.swift

@@ -9,6 +9,13 @@
 
 import CoreFoundation
 
+// WORKAROUND_SR????
+#if os(Windows)
+typealias _swift_CFThreadRef = HANDLE
+#else
+typealias _swift_CFThreadRef = pthread_t
+#endif
+
 internal class NSThreadSpecific<T: NSObject> {
     private var key = _CFThreadSpecificKeyCreate()
 
@@ -194,7 +201,7 @@ open class Thread : NSObject {
 
     open private(set) var threadDictionary: NSMutableDictionary = NSMutableDictionary()
 
-    internal init(thread: _CFThreadRef) {
+    internal init(thread: _swift_CFThreadRef) {
         // Note: even on Darwin this is a non-optional _CFThreadRef; this is only used for valid threads, which are never null pointers.
         _thread = thread
     }