Turn off front-camera workaround on iOS 6 or later

As discussed in #462, there are various problems with the workaround for corrupt images on iOS 5. Given that iOS 5 is quite legacy now, I think it's a reasonable solution to turn off that workaround if GPUImage is running on iOS 6 or later.

This could of course be adjusted if the precise version of the OS required for the workaround is not 5.X.
Fixed a problem where these 2 filters would not correctly set the frameSize through the forceProcessingAtSize: method
fixed gpuimage benchmark suite for live video streams
Merge pull request #1120 from paolonl/master

Fixed GPUImageAmatorkaFilter and GPUImageMissEtikateFilter not processing images at a desired size
Merge pull request #1103 from karlvr/front-camera-ios5-bug

Turn off front-camera workaround on iOS 6 or later
updated video processing benchmark - CoreImage processing now uses entire screen
Fixed a Mac build error introduced by a recent pull request.
Check that the session is running before trying to process frames - fixes crash when backgrounding app
Fix type in GPUImageHueFilter
Adding .svn to the ignore list for hybrid projects.
Marking the headers as 'public' so you can use the project as a direct dependency.
Adding missing rotation mode.
Fixing some of the exiting ones.
Fixing issue where the first frame would always be white because glUniform1i was failing after this switched shader programs unexpectedly due to the need to initialize the second filter.
Allow for chaining the output image size.
Re-working GPUImageVideoCamera to use the YUV->RGB transform method shown in Apple's AVBasicVideoOutput example because it produces results closer to that of the built-in camera.
Making GPUImageMovie do the YUV->RGB conversion via shader rather than asking AVFoundation to do it.
Update the view geometry on frame changes so we don't end up stretching the image if our view gets animated.
Don't enable the audio track if it's already enabled. It can cause the system to have two AVAssetWriters for audio going at once.
Lots going on here, but there was no logical way to separate it into smaller changes.

Allowing GPUImageMovie to take an AVPlayerItem for playback as well as an AVAsset in order to allow it to play AVComposition objects. When sourcing from an AVPlayerItem, it now uses CADisplayLink to handle the timing to ensure proper A/V sync.

Adding GPIImageMovieComposition specifically for reading from an AVCompostion object in non-real time. This is primarily so it can be connected to a GPUImageMovieWriter in order to render a composition to file.

Lots of changes to how audio/videoInputCallback(s) are managed to make rendering to a file reliable.
Moving target to iOS 6 so weak references will work as expected.
Merge branch 'master' of https://github.com/PedestrianSean/GPUImage