Buffer overrun in GMP 5.0.3

[Torbjorn Granlund]

We have a buffer overrun in GMP 5.0.3, furthermore the functions
affected are mpz_powm_sec and mpn_powm_sec, i.e. GMP's modexp functions
specifically recommended for cryptographic applications.

Extra safe turned extra unsafe with this release.

We will make a new release before the end of this week.

Only GMP 5.0.3 is affected; earlier GMP releases did not have this bug.

We apologise for the problems this creates.

-- 
Torbjörn