This bug fix release takes care of handful of problems that some users
have hit.  One recent bug, the others have been around a while.

Thanks to Jason Welstead for characterizing one bug and to Alex Gary for
fixing it.

Bug fixes:
 - Negative volume flag not working for Custom Geoms.
 - Crash on minimize/restore of main window on MacOS.
 - Mixed tolerances in CompGeom causing removal of watertight shapes.
 - Force true closure of six-series airfoils.