07cb422cbb
Some distributions (e.g. Fedora) added support for system wide crypto policies. This is supported in most common crypto libraries including OpenSSL. Applications can override this policy using their own cipher string. This commit adds support for specifying the cipher string in the mbsync configuration. For example, to exclude Diffie-Hellman, the user can specify CipherString "DEFAULT:!DH" in the IMAP Account's configuration.