Handling of Exception in sessionNofity call for HelloWorld example

This patch adds code to the HelloWorldClient implemenation which shows
how to handle Exceptions send by the stack to session.

Change-Id: I4191c08d7eeb2655813a4c0e89d4873d2dec41d1

git-svn-id: https://svn.apache.org/repos/asf/etch/trunk@1578902 13f79535-47bb-0310-9956-ffa450edef68
Fixing memory leak in handling of void functions

Void functions are handled differently from non-void functions. In case of
void functions the resulting mailbox has not been deleted which caused
memory leaks.

Change-Id: I2e44dacc9d632df0d06cc32c6ac868de5c74720d

git-svn-id: https://svn.apache.org/repos/asf/etch/trunk@1578903 13f79535-47bb-0310-9956-ffa450edef68