Fix rounding errors in easing functions.
Fix rounding errors in easing functions.

We also replace equality operations (which are troublesome in floating point)
with inequality comparisons.

easeInExpo/easeOutExpo/easeInOutExpo shouldn't under/overshoot their
targets now.

pixunil/cjs,magcius/gjs,joeshaw/gjs,djdeath/gjs,joeshaw/gjs,joeshaw/gjs,pixunil/cjs,mtwebster/cjs,mtwebster/cjs,magcius/gjs,joeshaw/gjs,pixunil/cjs,endlessm/gjs,djdeath/gjs,endlessm/gjs,mtwebster/cjs,mtwebster/cjs,endlessm/gjs,magcius/gjs,endlessm/gjs,djdeath/gjs,endlessm/gjs,djdeath/gjs,magcius/gjs,joeshaw/gjs,djdeath/gjs,mtwebster/cjs,pixunil/cjs,pixunil/cjs,magcius/gjs