Fix GPUImageTwoInputFilter to correctly reset itself
Remove weak reference when processing video to fix dealloc issue
Applied karlvr's suggested fix for the Lanczos resampling filter's renderTarget crash, based on pull request #880.
Merge pull request #905 from aburgel/fix_twoinput_filter

Fix GPUImageTwoInputFilter to correctly reset itself
Merge pull request #904 from aburgel/fix_weak_reference

Remove weak reference when processing video to fix dealloc crash
Added forceProcessingAtSizeRespectingAspectRatio: to GPUImageFilterGroup, per issue #870.