PolygonShape.set() calculates vertex uniqueness incorrectly

[ardabro]

Condition implemented as:
if (MathUtils.distanceSquared(v, ps[j]) < 0.5f * Settings.linearSlop)
should be:
if (MathUtils.distanceSquared(v, ps[j]) < (0.5f * Settings.linearSlop)*(0.5f * Settings.linearSlop))

Existing implementation leads to confusion.

[dmurph]

This matches the current Box2D implementation (see here: https://code.google.com/p/box2d/source/browse/trunk/Box2D/Box2D/Collision/Shapes/b2PolygonShape.cpp#141)

I stick to the Box2D implementation for all math and physics related code, unless there is an obvious bug that makes things explode. If you want this changed, you'll have to file an issue with Box2D. Sorry!