Merge branch 'master' into jgrpp

# Conflicts:
#	Makefile.src.in
#	findversion.sh
#	projects/determineversion.vbs
#	src/aircraft_cmd.cpp
#	src/lang/dutch.txt
#	src/linkgraph/linkgraph_gui.cpp
#	src/linkgraph/linkgraph_gui.h
#	src/order_cmd.cpp
#	src/settings_gui.cpp
#	src/smallmap_gui.cpp
#	src/town_cmd.cpp
#	src/viewport.cpp
#	src/water_map.h

src/main_gui.cpp

@@ -244,7 +244,7 @@ struct MainWindow : Window
 			return;
 		}
 
-		this->viewport->overlay->RebuildCache();
+		this->viewport->overlay->SetDirty();
 		this->GetWidget<NWidgetBase>(WID_M_VIEWPORT)->SetDirty(this);
 	}