Partial fix to limit when we do GL work to calls into framework, not a final solution
Postpone deleting invalid frames until we are permitted to do work in the GL context
Clarify multithreading requirements of SyphonClient in documentation
Remove use of CGLContext's lock in SyphonIOSurfaceImage
Merge pull request #4 from Syphon/mt-issue

Only perform GL work in API calls into the framework