Fix clang warnings / move some plat code into poly.

src/poly/cxx_compat.h

@@ -0,0 +1,25 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2014 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#ifndef POLY_POLY_CXX_COMPAT_H_
+#define POLY_POLY_CXX_COMPAT_H_
+
+// C++11 thread local storage.
+// http://en.cppreference.com/w/cpp/language/storage_duration
+#if XE_COMPILER_MSVC
+// VC++2014 may have this.
+#define thread_local __declspec(thread)
+#elif XE_LIKE_OSX
+// Clang supports it on OSX but the runtime doesn't.
+#define thread_local __thread
+#endif  // XE_COMPILER_MSVC
+
+namespace poly {}  // namespace poly
+
+#endif  // POLY_POLY_CXX_COMPAT_H_