> Not sure what meaning, if any, the 0 part has in the .so name here.

Right, it's probably better to fix the naming now.
The `0` has no sensible meaning in the .so name because we break ABI compatibility with every release.
I changed this to use 63 as major version instead. The trailing .2 makes the minor version and the patch level remains 0 for now.
So `2.064.2` would create `libphobos2.so.64.2.0`.

NB: [Semantic Versioning 2.0.0](http://semver.org/).