fix percentage roundtrip to odf

2014-03-10  Andreas J. Guelzow <aguelzow@pyrshep.ca>

	* openoffice-read.c (oo_date_text_append_quoted): new
	(oo_date_text_append_unquoted): new
	(oo_date_text_append): use the above
	(oo_date_text_end): use oo_date_text_append
	(odf_number_invisible_text): Quoting is now handled in
	oo_date_text_append