view: noclip version of int and float projection. Also project from behind the view's position and return coherent values for near clipping
transform: use the above functions for 2d center and helpline drawing
NOTE: the result for centers behind the camera (in perspective) isn't 100% perfect in the case of rotations because they always use the centered view vector as rotation axis and not the one aligned with the 2d center. Changing this would not be desirable anyway. At least it's predictible now.
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