Libxfce4ui api review, round 2

[Nick Schermer]

Maybe another worthy addition could be an implementation for
xselection checking for single instance applications. I think we use
this here and there...

gboolean
xfce_acquire_selection (const gchar *name, gboolean force,
GDestroyNotify callback_function, gpointer user_data, GError **error);

name: name of the selection.
force: force to get the selection.
callback_function: triggered when someone else took the selection, use
to quit this instance.
user_data: pointer for the GDestroyNotify callback.
error: Reason why false was returned (selection error or because the
selection was already acquired).
return value: %TRUE if selection was succesfully set, %FALSE if the
selection was already acquired or failed.

Duno about the GError parameter...

Nick