add GnomePrintJob to EvPrintJob constructor arguments.

add GnomePrintJob to EvPrintJob constructor arguments.

* shell/ev-window.c (ev_window_print): add GnomePrintJob to
EvPrintJob constructor arguments.

* backend/ev-ps-exporter.c, backend/ev-ps-exporter.h: interface
for documents that can export PostScript (page by page).

* backend/Makefile.am (libevbackend_la_SOURCES): add them.

* pdf/xpdf/pdf-document.cc (pdf_document_ps_export_begin)
(pdf_document_ps_export_do_page, pdf_document_ps_export_end)
(pdf_document_ps_exporter_iface_init:
Implement EvPSExporter.

* pdf/xpdf/Makefile.am (libxpdf_la_SOURCES): build PSOutputDev.