Problem with `string', threading and shared libraries.

[Benjamin Kosnik]

> | Can we start with adding the version number to the include directory paths?
> 
> I think that is the first step.

Note that there is support in the makefiles for this already, so all that 
needs to be done is turn it on by default.

I really think the symbol versioning is just as important though. 

A big first step would be to define the problem: what are the 
binary-incompatible flags? What symbols change? 

This just needs somebody, some time, and 'nm -A --demangle src/*.o'.
It would be nice to define a process too, so that each release could 
verify that it's doing the right thing.

It's at least a weeks worth of work, IMHO. 

-benjamin