Used by the routine at ENTER_ROOM.

Called when a room has been built (ENTER_ROOM). The exit code leaves a U or V of 0 or $FF as a marker of the wall he walked out through: 0 in U means he left by a wall at low U and comes in by this room's wall at high U, $FF the other way, and the same for V. He is put with his inner edge 2 inside the wall's line, the rest of him in the doorway, and ADJUST_PLYR_Z_FOR_ARCH finds the arch in that wall and stands him on its floor. Without a marker -- a new game, or a life started where he last came in -- he stays where his record says.

Both his records are flagged to be drawn, and the top is put at the legs' U and V. The walls are where the room's size puts them, so the doorway's place is worked out from ROOM_HALF_U and ROOM_HALF_V. As Knight Lore's adjust_plyr_xyz_for_room_size, with the same four U+V values for the arches.