tp_value_array_unpack: use a const string pointer in the example
tp_value_array_unpack: use a const string pointer in the example

This hopefully makes it a little more obvious that it isn't like
g_object_get, even if you're reading the example and ignoring the docs :-)

Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib,Distrotech/telepathy-glib