[bug] Pixel Aspect Ratio is not being saved on GIF files

[sd_snatcher]

The Pixel Aspect Ratio metadata is not being saved when images are converted to GIF.

Tested on XnConvert v1.77 on Mac OS-X v10.13.6.

Steps to reproduce

1) Add the two images attached here (Lenna2x1.png and ShouldBeSquare1x2.png) to the Input tab
2) Clear any actions present on the Action tab
3) On the output tab, check the "Preserve Metadata" checkbox
4) On the output tab, select the GIF file format
5) Proceed the conversion

The converted files will be missing the Pixel Aspect Ratio and will look distorted even on viewers that properly support Pixel Aspect Ratio, like XnViewMP.

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[xnview]

yes, currently this flag is not saved

[sd_snatcher]

Can it be implemented?