Fixes spelling in comment

resolve undeclared identifier close error

Fix for incorrect calcOpticalFlowPyrLK result evaluation with ARM NEON

UIImages with alpha were ending up with garbage pixels in background (random memory values).  Need to initialize matrix pixels before drawing UIImage with alpha on it.

Note: didn’t fix Grayscale image with alpha stripping alpha in UIImage -> Mat conversion.

Adding of destructor and placement new constructors for classes wrapped with CV_EXPORTS_W_SIMPLE macro