Add the contents of disk 1

- LHA -lh5/-lh6/-lh7 decoding with CRC checks (disk 1 is mostly lh5)
- Real track palettes and set names, read from each track file's header
- Camaro, plus the caravan as a towable trailer (Caravans option)
- Drivers' names, menu pictures and the original .set values per car
- Original sound effects (IFF 8SVX) through a new sample mixer: engine
  pitched with revs, tyre screech, crashes, backfire, horn, start beeps
- The original tune (OctaMED MMD1) through a new player; loudness tracks
  OpenMPT's render through the whole song. Music option in the menu
- Title picture (IFF ILBM) at the top of the menu
- skids unpack and skids music commands
- Gate crossings now judged on each car's whole movement per frame,
  including collision knocks; stalled computer cars are put back on the
  line after 8 seconds

The executable's game logic (handling, AI) is still not decoded.

assets/vehicles/caravan.txt

@@ -0,0 +1,23 @@
+# Skids vehicle settings. Lines starting with # are comments.
+# The sprite sheet is caravan.png: 32 headings across, 25 tilts down.
+name CARAVAN
+driver SIMON
+# yes = towed behind cars (Caravans option) instead of driven
+trailer yes
+# The 16 values from the original .set file. Their meaning is not
+# decoded yet, so the game does not use them; the handling below is
+# a reconstruction.
+original 2 65532 65532 1 12 10 16 14 0 0 0 0 0 0 0 0
+# top speed on tarmac, world pixels per second
+top 200
+# acceleration and braking, world pixels per second squared
+accel 170
+brake 320
+# sideways grip (higher = less sliding)
+grip 5
+# steering rate, radians per second
+turn 3.6
+# weight in collisions
+mass 1
+# speed and grip multiplier off the road
+offroad 0.55