ThreadPool is now adhoc available.

lib/std/threads/fixed_pool.c3

@@ -1,6 +1,8 @@
 module std::thread::threadpool @if (env::POSIX || env::WIN32);
 import std::thread;
 
+// Please do not use this one in production.
+
 fault ThreadPoolResult
 {
 	QUEUE_FULL

lib/std/threads/pool.c3

@@ -1,7 +1,7 @@
 module std::thread::pool(<SIZE>);
 import std::thread;
 
-struct ThreadPool
+struct ThreadPool @adhoc
 {
 	Mutex mu;
 	QueueItem[SIZE] queue;