Provide DH_check*_ex and many error codes

Provide DH_check*_ex and many error codes

DH_check{,_pub_key}_ex() wrap their non-ex versions to translate
the flags argument of the original functions into OpenSSL errors.
For this almost a dozen new error codes need to be added.

DH_params_check{,_ex}() is a new version of DH_check that only
performs a cheap subset of the checks.

They are needed to implement EVP_PKEY_{public,param}_check()
(observe the consistent naming) although the actual implementation
of EVP_PKEY_param_check() chose to use DH_check_ex().

As far as I can tell, the only raison d'être of the _ex functions
and error codes is to spew them to stderr in a couple of openssl(1)
commands. This couldn't have been solved differently...

These functions will not be exposed publicly.

ok inoguchi jsing