Merge pull request #250 from jcelerier/patch-1

Add an escape hatch when thread-local is not supported

Author: cameron314

concurrentqueue.h

@@ -104,7 +104,7 @@ namespace moodycamel { namespace details {
 	static const thread_id_t invalid_thread_id2 = 0xFFFFFFFFU;	// Not technically guaranteed to be invalid, but is never used in practice. Note that all Win32 thread IDs are presently multiples of 4.
 	static inline thread_id_t thread_id() { return static_cast<thread_id_t>(::GetCurrentThreadId()); }
 } }
-#elif defined(__arm__) || defined(_M_ARM) || defined(__aarch64__) || (defined(__APPLE__) && TARGET_OS_IPHONE)
+#elif defined(__arm__) || defined(_M_ARM) || defined(__aarch64__) || (defined(__APPLE__) && TARGET_OS_IPHONE) || defined(MOODYCAMEL_NO_THREAD_LOCAL)
 namespace moodycamel { namespace details {
 	static_assert(sizeof(std::thread::id) == 4 || sizeof(std::thread::id) == 8, "std::thread::id is expected to be either 4 or 8 bytes");