badguy.cpp: Badguys don't squish other badguys.

badguy.cpp: Badguys don't squish other badguys.

They still turn around when walking into one another, but Bouncy, Jumpy and
friends no longer squish their coworkers.

Badguys that madly wish to be squished by other badguys, should check if they
were hit from above in "collision_badguy" which is now called instead.

Some exception *might* be necessary for stalactites.

git-svn-id: http://supertux.lethargik.org/svn/supertux/trunk/supertux@6554 837edb03-e0f3-0310-88ca-d4d4e8b29345