take paper size and duplex setting parameters.
(init): add paper size and duplex parameters.
(writeDocSetup): add duplex parameter.

* poppler/PSOutputDev.h: update declarations.

* glib/poppler-private.h (struct _PopplerPSFile): store necessary
information to eventually construct a PSOutputDev.

* glib/poppler-page.cc (poppler_page_render_to_ps): initialize the
output dev if it doesn't exist yet.

* glib/poppler-document.cc (poppler_ps_file_new): don't create the
PSOutputDev here, just store filename and page range.
(poppler_ps_file_set_paper_size, poppler_ps_file_set_duplex): new
functions.
(poppler_ps_file_free): free the filename which we strdup now.

* glib/poppler-document.h: add prototypes.