I cannot reproduce this issue, it seems it fixed somehow by itself, after some full-upgrades I guess.
Sorry for bothering.
- Bug#876209: libgd3:i386 conflicts with libgd3:amd64 Vincas Dargis
- Bug#876209: [pkg-GD-devel] Bug#876209: libgd3:i386 conf... Ondřej Surý
- Bug#876209: Cannot reproduce Vincas Dargis
