Bug#693003: Bug#693002: libimager-perl: breaks libimager-qrcode-perl

[Tony Cook]

The only way I can see to fix this from my end is to have Imager build
a separate libimager.so.ABI[1].

For that to be useful though, I suspect packagers would need to
extract that libimager.so.ABI into a new package, which might be too
much effort for such a minor package.

I had planned to break the ABI again with the thread safety changes
coming up, but this issue has me reconsidering that.

Tony

[1] complicated by support for Win32 builds