Environment: Time of day fixes and add serverside getter

-> Put access to time variables under the time lock.
-> Merge both time locks, there is no point to have two locks.
-> Fix the lock being released too early in Environment::setTimeOfDay
-> Add serverside getter so that you don't have to get
	the environment if you only have the server

src/server.cpp

@@ -1249,6 +1249,11 @@ void Server::setTimeOfDay(u32 time)
 	m_time_of_day_send_timer = 0;
 }
 
+u32 Server::getTimeOfDay()
+{
+	return m_env->getTimeOfDay();
+}
+
 void Server::onMapEditEvent(MapEditEvent *event)
 {
 	if(m_ignore_map_edit_events)