Merge branch 'camera-fix' into 'next'

Camera fix

This fixes the third person camera being silly around intangible PolyObjects, particularly the fact they can affect the camera's floorz and ceilingz even though I see no reason why they should do so.

Also a good reminder that POF_SOLID is the same as POF_CLIPLINES and POF_CLIPPLANES combined, which is probably how this issue came about to begin with. Can't say that with certainty of course.

See merge request !57