Add callback parameter for core.emerge_area()

src/server.h

@@ -378,6 +378,9 @@ class Server : public con::PeerHandler, public MapEventReceiver,
 	// Bind address
 	Address m_bind_addr;
 
+	// Environment mutex (envlock)
+	Mutex m_env_mutex;
+
 private:
 
 	friend class EmergeThread;
@@ -518,7 +521,6 @@ class Server : public con::PeerHandler, public MapEventReceiver,
 
 	// Environment
 	ServerEnvironment *m_env;
-	Mutex m_env_mutex;
 
 	// server connection
 	con::Connection m_con;