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.
Undid pull request #905, because it broke blends in many cases.
Fix filter resetting to ensure GPUImageTwoInputFilter is in good state
Started Mac port, so restructuring things to support this. Mac test application somewhat functional.
Added a FilterShowcase example to the Mac port and added an AV Foundation video camera input to the Mac.
Ported several filters to the Mac, along with some base classes. Expanded the FilterShowcase Mac example.
Ported another set of filters to the Mac.
Ported the blend filters to the Mac.
Fixed a crashing bug in the crop filter on iOS.
Ported a few more color adjustment filters to the Mac. Tweaked the way that GPUImageView works on the Mac to support resizing correctly.
Added a multiview test for the Mac. For now, locking focus on views to prevent glitches with multiple NSOpenGLViews on the Mac.
Added the lookup filters. Fixed some things I broke in the last commit on the Mac.
Ported convolution filters to the Mac and added a Laplacian filter.
Added a three-input filter type, fixed scaling issues with the Lanczos resampling, and started adding multiple AV camera support to the Mac.
Added build.sh to produce a universal iOS library