Add runtime/bin/thread_fuchsia that binds to fuchsia's pthreads

runtime/bin/thread_fuchsia.h

Index: runtime/bin/thread_fuchsia.h
diff --git a/runtime/bin/thread_android.h b/runtime/bin/thread_fuchsia.h
similarity index 90%
copy from runtime/bin/thread_android.h
copy to runtime/bin/thread_fuchsia.h
index 2551c01804935c13061296559717f6669293c9b7..57cc0896261af0c901e79cb191fa22a202b13e2c 100644
--- a/runtime/bin/thread_android.h
+++ b/runtime/bin/thread_fuchsia.h
@@ -2,11 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#ifndef BIN_THREAD_ANDROID_H_
-#define BIN_THREAD_ANDROID_H_
+#ifndef BIN_THREAD_FUCHSIA_H_
+#define BIN_THREAD_FUCHSIA_H_
 
 #if !defined(BIN_THREAD_H_)
-#error Do not include thread_android.h directly; use thread.h instead.
+#error Do not include thread_fuchsia.h directly; use thread.h instead.
 #endif
 
 #include <pthread.h>
@@ -74,4 +74,4 @@ class MonitorData {
 }  // namespace bin
 }  // namespace dart
 
-#endif  // BIN_THREAD_ANDROID_H_
+#endif  // BIN_THREAD_FUCHSIA_H_