CreatePerspectiveFieldOfView throws in valid cases

CreatePerspectiveFieldOfView, both in Matrix4 and Matrix4d, probably should not throw when zNear is greater than zFar. Sometimes, a user will want this. For example, to minimize the impact of depth buffer precision lost for distance objects, it is common to swap the traditional near/far values, change the depth test from less to greater than, and use a 32-bit floating point depth buffer. For more information see http://outerra.blogspot.com/2009/12/floating-point-depth-buffer.html.