long long

[Torbjorn Granlund]

I suspect few people would get any joy if we extended the range from 32
bits to 64 bits under Windoze.  I think I never passed a constant
argument >100 to any _ui functions.

Code relying on _ui constants >= 2^32 is not portable between 32-bit
systems and 64-bit systems, btw.

Using mp_limb_t for user provided constants poses the problem of how to
portably define those.  Should they use an 'l' or an 'll' suffix?  It
also introduces incompatibility, so if we decide for suh a change, we
should do it at the same time as other incompatibe changes.  (I listed
such possible changes at a web page recently, cannot recall its URL
right now.)

We could perhaps add a parallel set of functions (_ul, or _ull) allowing
long long.  We should then follow the principle of "one GMP release, one
GMP API" and reject compilers and ABIs without long long support.

-- 
Torbjörn