Backport regression test

master branch has a specific regression test for a bug in x86_64-mont5 code,
see commit cdfe0fdde6a966bdb0447de66aa04a85d99a0551.

This code is now in 1.0.2/1.0.1, so also backport the test.

Reviewed-by: Richard Levitte <levitte@openssl.org>