Thread: make Thread.name return the current thread name

This makes the `name` property use the CoreFoundation SPI to query the
thread name to avoid having to have this interface be used directly in
the tests.

Author: compnerd

Foundation/Thread.swift

@@ -255,6 +255,14 @@ open class Thread : NSObject {
         }
     }
 
+    public var _name: String? {
+      var buffer: [Int8] = Array<Int8>(repeating: 0, count: 128)
+      if _CFThreadGetName(&buffer, Int32(buffer.count)) == 0 {
+        return nil
+      }
+      return String(cString: buffer)
+    }
+
 #if os(Windows)
     open var stackSize: Int {
       get {

TestFoundation/TestThread.swift

@@ -54,18 +54,7 @@ class TestThread : XCTestCase {
 
         // Compare the name set in pthreads()
         func compareThreadName(to name: String) {
-            var buf = [Int8](repeating: 0, count: 128)
-#if os(macOS) || os(iOS)
-            // Dont use _CF functions on macOS as it will break testing with Darwin's native Foundation.
-            let r = pthread_getname_np(pthread_self(), &buf, buf.count)
-#else
-            let r = _CFThreadGetName(&buf, Int32(buf.count))
-#endif
-            if r == 0 {
-                XCTAssertEqual(String(cString: buf), name)
-            } else {
-                XCTFail("Cant get thread name")
-            }
+            XCTAssertEqual(Thread.current._name, name)
         }
 
         // No name is set initially