Use g_set_error_literal now that we depend on glib 2.18.

Use g_set_error_literal now that we depend on glib 2.18.

	* backend/comics/comics-document.c: (comics_document_load):
	* backend/djvu/djvu-document.c: (djvu_document_load):
	* backend/dvi/dvi-document.c: (dvi_document_load):
	* backend/impress/impress-document.c: (impress_document_load):
	* backend/pdf/ev-poppler.cc:
	* libdocument/ev-document-factory.c: (get_document_from_uri),
	(ev_document_factory_get_document):
	* shell/ev-print-operation.c:
	(ev_print_operation_export_print_dialog_response_cb): Use
	g_set_error_literal now that we depend on glib 2.18.

svn path=/trunk/; revision=3419