putty: security bump to version 0.71

putty: security bump to version 0.71

CVE-2019-9894: A remotely triggerable memory overwrite in RSA key
exchange can occur before host key verification.

CVE-2019-9895: A remotely triggerable buffer overflow exists in any kind
of server-to-client forwarding.

CVE-2019-9897: Multiple denial-of-service attacks that can be triggered
by writing to the terminal.

CVE-2019-9898: Potential recycling of random numbers used in
cryptography.

Disable static build for now. When building statically configure defines
NO_GSSAPI. Build with NO_GSSAPI is currently broken. The issue has been
reported upstream.

Cc: Alexander Dahl <post@lespocky.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>