tr2/objects/gondola: save gondola position

This updates gondola objects to have their positions saved in order to
be able to restore them correctly on load when they've been destroyed.
Legacy saves will ignore this.

Resolves #1612.

docs/tr2/CHANGELOG.md

@@ -41,6 +41,7 @@
 - fixed invalid portals in The Deck between rooms 17 and 104, which could result in Lara seeing enemies in disconnected rooms (#2393)
 - fixed pushblocks being rotated when Lara grabs them, most noticeable if asymmetric textures have been used (#2776)
 - fixed the boat briefly having an underwater hue when Lara first climbs on (#2787)
+- fixed destroyed gondolas appearing embedded in the ground after loading a save (#1612)
 - fixed the camera going out of bounds in 60fps near specific invalid floor data (known as no-space) (#2764, regression from 0.10)
 - fixed sprites rendering black if no shade value is assigned in the level (#2701, regression from 0.8)
 - fixed some 3D pickup items rendering black in software mode (#2792, regression from 0.10)

docs/tr2/README.md

@@ -246,6 +246,7 @@ as Notepad.
     - fixed Floating Islands mystic plaque inventory rotation
 - fixed pushblocks being rotated when Lara grabs them, most noticeable if asymmetric textures have been used
 - fixed being able to use hotkeys in the end-level statistics screen
+- fixed destroyed gondolas appearing embedded in the ground after loading a save
 - improved the animation of Lara's braid
 
 #### Cheats