2, 3 or 4 digit iMesh version number

[Jason Kraftcheck]

Mark Miller wrote:
> Hi All,
> 
> Last week we talked about the fact that, technically speaking, we should
> only ever need a 2 digit version number for iMesh because it is really
> just an interface specification. Other than the header file itself,
> there is no real code to version. However, we agreed that a 3rd, patch
> digit which ordinarily applies only to bug fix releases of code
> underpinning an interface, gives us finer control over the version
> number and has value just for that reason.
> 
> I'd like to raise the possibility of a 4th digit.
> 

Another possible solution is to have a two-value ABI version number that is
separate from the interface/API version number that is used for releases,
documentation, etc.  This way the ABI version numbers used for compatibility
would be entirely functional.  We could do things like increment the
appropriate ABI version value with *every* check-in of changes to the headers.

- jason