[Patch] Remove fpos<>::operator== and !=

[Paolo Carlini]

Mark Mitchell wrote:

>I don't know exactly what source/binary constraints libstdc++ is
>operating under, but that seems like an incompatible change, as
>"pos::operator==(-1)" will presumably no longer work?
>
Indeed, the standard only requires operator== on those objects being an 
equivalence relation. The requirements are generally very, very, loose. 
In any case, there are quite a few comments in the file, with specific 
citations to the standard.

Actually, I'm pretty sure that the definition of that operator is a loft 
over from a preliminary implementation of the class, when streamoff was 
of class type (I followed the development of this specific code).

Paolo.