lex
    Qu   - for 'd' or 'v', compute upper hull without point at-infinity
              returns furthest-site Delaunay triangulation
    Qv   - test vertex neighbors for convexity
    Qx   - exact pre-merges (skips coplanar and anglomaniacs facets)
    Qz   - add point-at-infinity to Delaunay triangulation
    QGn  - good facet if visible from point n, -n for not visible
    QVn  - good facet if it includes point n, -n if not
    Q0   - turn off default p remerge with 'C-0'/'Qx'
    Q1     - sort merges b