* bignum.c (bary_mul_gmp): Use mpz_init and mpz_clear instead of
  mpz_inits and mpz_clears.
  Older GMP don't have them.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42761 b2dd03c8-39d4-4d8f-98ff-823fe69b080e