* os400: minimum supported OS version is now V6R1.
Do not log compiler informational messages.
* Implement crypto backend specific Diffie-Hellman computation.
This feature is now needed on os400 because the QC3 library does not
implement bn_mod_exp() natively. Up to now, this function was emulated using
an RSA encryption, but commits ca5222ea81 and
7934c9ce2a (CVE-2016-0787) broke the emulation
because QC3 only supports RSA exponents up to 512 bits.
Happily, QC3 supports a native API for Diffie-Hellman computation, with
opaque random value: this commit implements the use of this API and, as a
side effect, enables support of this feature for any other crypto backend that
would use it.
A "generic" Diffie-Hellman computation internal API supports crypto backends
not implementing their own: this generic API uses the same functions as before.
* Fix typos in docs/HACKING.CRYPTO.
