introduced by the bsp routines. It's usually, though not always,
possible to generate a watertight mesh. The occasions where it's
not look ugly, floating point issues, no quick fix.
And use those to generate a list of edges where two different faces
meet, which I can emphasize for cosmetic reasons (and some UI to
specify whether to do that, and with what color).
And make the right mouse button rotate the model, since that was
previously doing nothing.
[git-p4: depot-paths = "//depot/solvespace/": change = 1821]
Jonathan Westhues