vector2d::equals now has an tolerance parameter for passing the epsilon (like vector3d has already). Note that this changes the default behavior of vector2d::equals as well as functions using it like the operators for ==, !=, <, >, <=, >= when using vector2d with f64 as the tolerance is increased in that case (for f32 and integer values it shouldn't make any difference).

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@4584 dfc29bdd-3216-0410-991c-e03cc46cb475