Move upstream saveload to src/saveload/, move jgrpp saveload to src/sl/

Leave afterload in src/saveload/

src/saveload/CMakeLists.txt

@@ -1,4 +1,4 @@
-add_subdirectory(upstream)
+add_subdirectory(compat)
 
 add_files(
     afterload.cpp
@@ -6,17 +6,13 @@ add_files(
     airport_sl.cpp
     animated_tile_sl.cpp
     autoreplace_sl.cpp
-    bridge_signal_sl.cpp
     cargomonitor_sl.cpp
     cargopacket_sl.cpp
     cheat_sl.cpp
     company_sl.cpp
-    debug_sl.cpp
     depot_sl.cpp
     economy_sl.cpp
     engine_sl.cpp
-    extended_ver_sl.cpp
-    extended_ver_sl.h
     game_sl.cpp
     gamelog_sl.cpp
     goal_sl.cpp
@@ -29,33 +25,16 @@ add_files(
     misc_sl.cpp
     newgrf_sl.cpp
     newgrf_sl.h
-    newsignals_sl.cpp
     object_sl.cpp
-    oldloader.cpp
-    oldloader.h
-    oldloader_sl.cpp
     order_sl.cpp
-    plans_sl.cpp
     saveload.cpp
     saveload.h
-    saveload_buffer.h
-    saveload_common.h
-    saveload_filter.h
-    saveload_internal.h
-    saveload_types.h
-    signal_sl.cpp
+    settings_sl.cpp
     signs_sl.cpp
     station_sl.cpp
     storage_sl.cpp
-    strings_sl.cpp
     story_sl.cpp
     subsidy_sl.cpp
-    tbtr_template_replacement_sl.cpp
-    tbtr_template_veh_sl.cpp
     town_sl.cpp
-    tracerestrict_sl.cpp
-    train_speed_adaptation.cpp
-    tunnel_sl.cpp
     vehicle_sl.cpp
-    waypoint_sl.cpp
 )