[Inkscape-devel] Stable 0.92.1 and gcc-7

I know that trunk has been cleaned up for gcc-7, but some of us prefer to build rleases. The following patch (backported from trunk, boy, do I hate bazaar ;) fixed the errors I was getting.

Now, I don't have all the possible deps, so it might be that there are other problems I haven't seen, but maybe this will help someone.

ĸen