openssl: improve logging

openssl: improve logging

This improves OpenSSL logging and removes OpenSSL-specific error
printing code from error.c. The crypto_msg() functions provide
convenience wrappers, specific to OpenSSL. Instead of passing the
magical 'M_SSLERR' flag to msg(), a developer now just calls
crypto_msg() to get OpenSSL errors dumped to log.

This is commit is a combined cherry-pick of commits e795d6ba and
98ea2ec5 from the master branch, adjusted to the release/2.3 branch.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1452113464-28062-2-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/10944
Signed-off-by: Gert Doering <gert@greenie.muc.de>