Fix filter resetting to ensure GPUImageTwoInputFilter is in good state
Fixed issue #765

- Added 'cancelProcessing' method to GPUImageMovie to cancel an on-going video file processing.
- Added a check to cancelled status to 'finishRecordingWithCompletionHandler:' in GPUImageMovieWriter to detect if the writing was cancelled.
Fix GPUImageRawDataOutput so that if the current frame has been read previously, the cached version is returned rather than reading the pixel buffer/texture cache each time
Fixed vignette filter to take into account alpha in the original image, improved its performance.
Merge pull request #935 from aburgel/better_twoinput_fix

Fix filter resetting to ensure GPUImageTwoInputFilter is in good state
Merge pull request #970 from stevegraham/raw-data-output-fix

Use GPUImageRawDataOutput cached bytes
Merge pull request #964 from jvaldera/master

Fixed issue #765
Ported the corner and line detectors to the Mac. Fixed a glitch in the line detector.
Added alpha support to the RGB and polka dot filters.
Ported the buffer-based filters to the Mac, although I need to fix the motion detector display.
Ported the remaining filters to the Mac. Dramatically improved quality of the Gaussian blur by fixing an idiotic swap of texel offsets that I had in there for most of a year.
bugfix
Merge pull request #986 from DrMoriarty/upstream

Trivial bugfix
Attempting to protect against improper deallocation of resources outside of the image processing OpenGL ES context.