Add openfloorrover and openceilingrover vars so that PIT_CheckLine can update...

Add openfloorrover and openceilingrover vars so that PIT_CheckLine can update tmfloorrover and tmceilingrover properly via P_LineOpening

...which should hopefully stop that issue where you just teleport back to the ground. Assuming this works as expected.

Also this is untested lol.