construct io_context with the hints that it's single-threaded

simulation/libsimulator

@@ -1 +1 @@
-Subproject commit e4fb5e171a6ed885e7de3192153ba77835d23dee
+Subproject commit ba65f2fc25cb0cf6ab141102952b9c5c54f02c41

src/session.cpp

@@ -326,7 +326,7 @@ namespace {
 		if (internal_executor)
 		{
 			// the user did not provide an executor, we have to use our own
-			m_io_service = std::make_shared<io_service>();
+			m_io_service = std::make_shared<io_service>(1);
 			ios = m_io_service.get();
 		}