QPID-5133: Add option to the spout examples to enable durable messages

Each of the examples (C++, Ruby, Perl, Python) now have a command line
option to set the durable flag on messages sent. This allows for
experimenting with message persistence.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1522042 13f79535-47bb-0310-9956-ffa450edef68