Changes:
Copy the startup-id string, not just the pointer
The fix for the memory leak of commit fd7aaf0e exposed the fact
that we did not copy the startup notification id across messages,
but we simply stored the pointer.
This commit should fix the double-free errors happening to
applications using libunique.
Unique is a library for writing single instance application. If you launch a
single instance application twice, the second instance will either just quit or
will send a message to the running instance.
Unique makes it easy to write this kind of applications, by providing a base
class, taking care of all the IPC machinery needed to send messages to a
running instance, and also handling the startup notification side.
Unique aims to replace the BaconMessageConnection code that has been copied by
many projects and the code using Bonobo and D-Bus.
