dispatch: use platform specific paths for setting thread names

This adds the Windows specific path for setting the thread name.  This
may only work partially as the thread name is meant to be UCS-2, but for
now, matches the behaviour in Foundation.

Similarly, on Linux, `pthread_setname_np` takes a thread identifier to
set the name.  Add a platform specific path here as well.

Author: compnerd

src/queue.c

@@ -6988,7 +6988,19 @@ _dispatch_worker_thread(void *context)
 	/* Set it up before the configure block so that it can get overridden by
 	 * client if they want to name their threads differently */
 	if (dq->_as_dq->dq_label) {
+#if defined(__APPLE__)
 		pthread_setname_np(dq->_as_dq->dq_label);
+#elif defined(_WIN32)
+		int length = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, dq->_as_dq->dq_label, -1, NULL, 0);
+		if (length) {
+			WCHAR *description = calloc(length + 1, sizeof(WCHAR));
+			MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, dq->_as_dq->dq_label, -1, description, length);
+			SetThreadDescription(GetCurrentThread(), description);
+			free(description);
+		}
+#else
+		pthread_setname_np(pthread_self(), dq->_as_dq->dq_label);
+#endif
 	}
 
 	if (pqc->dpq_thread_configure) {