Fix FloatUtil.makePerspective(..): The tan(fovy/2) shall be used, not tan(fovy), fix callers; Simplify FloatUtil.makePerspective(..FovHVHalves..)

Fix FloatUtil.makePerspective(..): The tan(fovy/2) shall be used, not tan(fovy), fix callers
 - This bug didn't hit (yet), since callers already performed the division (degree -> radian)
   by falsly claiming the passed value is in radian - where it was actually fov/2 in radians.

Simplify FloatUtil.makePerspective(..FovHVHalves..)
 - Due to the fix above, it became pretty clear that the makeFrustum(..)
   method can be utilized.
   Simply apply all our tan-half-fov values on zNear.