JIRA-4372: Added a CMakeLists.txt file for messaging examples.

In the messaging/dist_extra directory is a CMakeLists.txt file that will
be shipped under both the autotool and cmake builds with the messaging
examples.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1435129 13f79535-47bb-0310-9956-ffa450edef68