Fixed thread pool a bit

Use 128-bit allocator instead of queue.
When pool is full (128), threads just terminate as before.

rpcs3/Emu/CPU/CPUThread.cpp

@@ -522,6 +522,8 @@ void cpu_thread::operator()()
 
 			s_tls_thread_slot = -1;
 
+			g_tls_current_cpu_thread = nullptr;
+
 			_this = nullptr;
 		}