[m-dev.] For review: base_type_layouts, round 2.

[Tyson Richard DOWD]

> > 
> > Will this cause binary incompatibilities?
> > (i.e. once you commit it, will everyone have to do `mmake clean'?)
> > 
> 
> Yes - you'll get link errors unless you recompile everything. 
> 

Oops, I lied. Because base_type_functors are only referred to by 
base_type_infos, and base_type_infos are generated when functors are,
you won't get link errors. Instead, you'll probably get core dumps if
you try to read the typenames, since they are not at the old offset
anymore. 

So the moral of the story is - if you use functor, arg, expand,
deep_copy, io__write, or your own C code that uses base_type_*, 
and things core dump, `mmake clean' and rebuild before reporting a bug.