mpz_gcd_ext(NULL, ...)

[Marc Glisse]

Hello,

a user was asking if we could support calling mpz_gcd_ext with a NULL 
first argument (the gcd), since they are only interested in the 
coefficients s and t and would like to save the unnecessary allocation. I 
doubt it would save that much, but it seems trivial to add a check 
if(g!=NULL) similar to the tests for s and t. Does it make sense to you?

-- 
Marc Glisse