Add a hack to work around path change problems

Add a hack to work around path change problems

The path timing code is crap overall; it uses rounded floats for time
calculations that really should be exact, and path parts can change in
the middle of a time step. The latter causes visible problems on the
centrifuge test map; probably similar problems would be reproducible
for linear movement on a suitable map (perhaps a platform that quickly
descends at a constant speed over multiple path parts). Add a hack to
work around this by splitting movements if they'd continue over path
part changes.

From: Uoti Urpala

git-svn-id: https://s.snth.net/svn/neverball/trunk@3323 78b8d119-cf0a-0410-b17c-f493084dd1d7