python3: do not use the system OpenSSL in the host variant

python3: do not use the system OpenSSL in the host variant

host-python3 currently detect if there is an usable OpenSSL installation
and conditionnaly compiles the 'ssl', '_ssl' and '_hashlib' modules.
This may break compilation if the system's OpenSSL has been updated to
1.1.0 because of a bug in python, see https://bugs.python.org/issue26470
for details.

Unlike Python 2.7, Python 3 unconditionnaly compiles fallbacks for
common hash algorithm, so disabling OpenSSL will still leave Python 3
with implementations of common hash algorithm.

This adds a patch to configure.ac patch to implement a --disable-openssl
option.

Signed-off-by: Nicolas Cavallari <nicolas.cavallari@green-communications.fr>
Tested-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>