Find this kind of bug is definitely out of my juridiction - please, PLEASE maintain a list of changes to apply on each port. Having negative elapsed time messed the animations so weird that you can't guess where that came from.

git-svn-id: https://svn.code.sf.net/p/freeglut/code/trunk/freeglut@1625 7f0cb862-5218-0410-a997-914c9d46530a