QPID-4885: C++ examples install to qpid/examples

Previously they installed to /usr/local/share/examples. This changes
that to /usr/local/share/qpid/examples instead.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1486084 13f79535-47bb-0310-9956-ffa450edef68