(Java_java_math_BigInteger_modpow0): mpz_powm() does not work with negative exponent. (Java_java_math_BigInteger_modinv0): convert negative remainder to positive equivalent. This fix Volano License bug.
(Java_java_math_BigInteger_modpow0): mpz_powm() does not work with
negative exponent.
(Java_java_math_BigInteger_modinv0): convert negative remainder to
positive equivalent.
This fix Volano License bug.

kaffe/kaffe,kaffe/kaffe,kaffe/kaffe,kaffe/kaffe,kaffe/kaffe