Apply patch from Bas Wijnen preventing the player from getting the Jetpack too early.

Apply patch from Bas Wijnen preventing the player from getting the Jetpack too early.

From: Bas Wijnen <wijnen@debian.org>

Attached is a version of data/hub which implements the level order as I
consider it appropriate.  I reorganized and reindented the file, because
it wasn't clearly readable to me.  The actual changes aren't large
though.  What I did:

- Set the requirement for "Ancient Tomb #4" from "BioMech Assimilator"
  to "Stages 18"
- Set the requirement for "BioMech Assimilator" from "Stages 15" to
  "Ancient Tomb #4".

I have tested this using cheat mode, pressing F3 to finish all levels,
and it works as expected.