C implementation of mod_1_1

[Torbjorn Granlund]

Torbjorn Granlund <tg at gmplib.org> writes:

  Torbjorn Granlund <tg at gmplib.org> writes:
  
    This bug is triggered by a recent change, but not necessarily your
    division changes.
    
  The bug is triggered by my mz/givegcd.c change.

I have pushed a fix for this week-old bug now.  The problem was my
passing of an mp_limb_t to an mpz _ui function.  The code now uses the
correpsonding mpn function instead.

I also did a cleanup of mpz/divegcd.c as per Marc Glisse's suggestion.

-- 
Torbjörn