Move m_level_ends_if_killed to cEnemy

[Quintus]

The m_level_ends_if_killed member currently only exists for specific enemies, namely the furball boss and the turtle boss. While for normal gameplay this is fine, for scripting it would be much more interesting to have the level end when any given enemy is killed, e.g. a spika or so. This requires the m_level_ends_if_killed member to be moved directly into the cEnemy class and merging the slightly different code currently in use in the cFurball and cTurtleBoss classes into one common place.

Vale,
Quintus

[Quintus]

Will not implement this. You can easily make the level end using scripting like this:

UIDS[14].on_die do
  Level.finish
end

So, the only reason we need m_level_ends_if_killed for is having e.g. the black furball not end the level when it is killed.

Vale,
Quintus