Duke3D: Shrunk state allows moving through much tighter spaces than before

Ever since the big clipping changes, it is now possible to move into much tighter spaces than before while shrunk.

Map to demonstrate: tightshrunk.map

The path on the right can be moved through since r7428 (d060ca95).

The path on the left can be moved into since r8568 (86b57410), and this particular path instantly kills the player despite being shrunk.