Renamed [xmin, ymin, xmax, ymax] in Bbox to [x0, y0, x1, y1] and
provide functions that really do give xmax etc. as well. Renamed lbrt to extents and lbwh to bounds (for consistency). Removed some dead code.
Authored by: mdboom 2007-10-24
Parent: [r3996]
Child: [r3998]