keep a reference to the source buffer while the clipboard contents buffer

keep a reference to the source buffer while the clipboard contents buffer

2006-04-28  Michael Natterer  <mitch@imendio.com>

	* gtk/gtktextbuffer.c (create_clipboard_contents_buffer): keep a
	reference to the source buffer while the clipboard contents buffer
	exists, because it is needed for serializing the contents buffer.
	Makes copying from the contents buffer possible even after the
	resp. text view is destroyed (for example when there is a
	clipboard manager running on app exit) (bug #339195).