Merge pull request #534 from est77/master

Fix compile error.
appleseed.package.py 2.3.10: improved robustness on Windows.

sometimes Windows will lock some files (while indexing?), preventing directories from being deleted.
Merge branch 'master' of github.com:appleseedhq/appleseed
fixed type mismatches.
minor code tweak.
Merge remote-tracking branch 'upstream/master' into OSL_emission
Experimenting with closure keywords.