Floor portal test, ported

src/deh_tables.c

src/info.c

src/info.h

src/p_mobj.c

src/p_setup.c

src/r_bsp.c

src/r_defs.h

src/r_main.c

src/r_plane.c

src/r_plane.h

src/r_portal.c

src/r_portal.h