giflib changes their API too much for unnecessary reasons. Nearly every recent release has needed source changes in the applications using it.
The latest example is the 5.1.0 release. The CloseFile functions were extended with a second argument. It would have been easy to do this in a backwards-compatible way: Just add a new function that has the additional argument, let's say DGifCloseFileError, and make DGifCloseFile a wrapper like:
return int DGifCloseFileError(GifFile, NULL);
I'm not expecting you to change this now, but please, please take more care of backwards compat in the future.