AFAICS, we don't have a default cipher suite but depend on openssl's default.

Document the fact that this default depends on the openssl version.
Recommend !aNULL over !ADH, because the former also excludes !AECDH in openssl
1.0+


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1135241 13f79535-47bb-0310-9956-ffa450edef68