Save a copy implemented for various backends.

Save a copy implemented for various backends.

	* configure.ac:
	* djvu/djvu-document.c: (djvu_document_load), (djvu_document_save),
	(djvu_document_finalize):
	* dvi/dvi-document.c: (dvi_document_load), (dvi_document_save),
	(dvi_document_finalize):
	* pixbuf/pixbuf-document.c: (pixbuf_document_load),
	(pixbuf_document_save), (pixbuf_document_finalize):
	* tiff/tiff-document.c: (tiff_document_load), (tiff_document_save),
	(tiff_document_finalize):

	Save a copy implemented for various backends.