GMP prototypes

[Marc Glisse]

On Wed, 17 Jul 2013, Marc Glisse wrote:
> On Tue, 16 Jul 2013, Torbjorn Granlund wrote:
>> I did not fix the C++ stuff, since I am less sure what is right there.
>
> AFAICT there are only 6 const needed, for operator<< and for the 
> constructors. I'll add them later.

Done. I noticed a couple things in the doc:

* we say that gmpxx requires gcc-2.91+ but I am not even sure we tested 
the latest release with gcc-2.95, it is probably better to just remove 
this precision and stick to "reasonably recent".

* we document get_mpz_t as returning an mpz_t (it returns an mpz_ptr), 
which could confuse users since IIRC we explain elsewhere that one cannot 
return an mpz_t. I hesite between: 1) do nothing, 2) document a return 
type of mpz_t& even though that's a lie, and 3) something else. 1) for now 
;-)

-- 
Marc Glisse