* buffer.c (Fmake_overlay, Fmove_overlay): New optional BUFFER

* buffer.c (Fmake_overlay, Fmove_overlay): New optional BUFFER
	arguments.
	(recenter_overlay_lists): New argument BUF, to use instead of the
	current buffer.
	(Foverlay_recenter): Pass the appropriate arguments to
	recenter_overlay_lists.

	* buffer.c (Fdelete_overlay): Don't assume that overlay is in the
	current buffer.  Don't forget to declare the argument a Lisp_Object.