libfreenect v0.6.4 Dwelling

• fix(c_sync): unlock when returning early - fixes #641
• fix: silence incorrect audio serial warning to close #657
• build(examples): modernize opengl imports to close #658 and close #661 by @piedar in #663 (thanks @mpictor and @jlblancoc for initial patches)

Full Changelog: v0.6.2...v0.6.4