Add authz providers for use with mod_authz_core and its RequireAny/RequireAll

containers:

'ssl' (equivalent to SSLRequireSSL)
'ssl-verify-client' (for use with 'SSLVerifyClient optional')
'ssl-require' (expressions with same syntax as SSLRequire)

We may decide to axe 'ssl-require' again in favor of the generic 'expr'
provider, depending on the development of the ap_expr parser.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1002837 13f79535-47bb-0310-9956-ffa450edef68