NO-JIRA: Detect lack of proton SSL support

- Dispatch: log an error and don't complete SSL connection if no SSL support.
- System tests: Skip SSL tests if SSL support is not available.

Note: the error handling for SSL connections in dispatch still needs work.

git-svn-id: https://svn.apache.org/repos/asf/qpid/dispatch/trunk@1610744 13f79535-47bb-0310-9956-ffa450edef68