Version consistency checks (v3.0.x and master)

[Alan DeKok]

Phil Mayers wrote:
> And the dictionaries. Maybe a special comment:
> 
> # dict version=x.x

  That's possible.  The simplest thing is to update a special value in
the dictionary files.  It's awkward, but really only necessary for every
release.

> The answer is probably "no that's crazy" but I don't suppose ABI /
> symbol versioning helps here?

  Some.  The issue is that we make changes to internal data structures.
 So the old libraries aren't really compatible with the new binaries.
The typical library versioning approach isn't fine-grained enough.  And
symbol versioning doesn't deal with changes to data structures.

  Alan DeKok.