fix framework detection


git-svn-id: https://geuz.org/svn/gmsh/trunk@17521 59c8cabf-10d6-4a28-b43f-3936b85956c4
call setVolumePositive after mesh optimization, as the optimizer can revert elements


git-svn-id: https://geuz.org/svn/gmsh/trunk@17522 59c8cabf-10d6-4a28-b43f-3936b85956c4