add GMutex (not used yet)

add GMutex (not used yet)

* xpdf/gpdf-g-switch.h: add GMutex (not used yet)

* shell/gpdf.c (gpdf_window_new): s/gtk_type_new/g_object_new/,
use construction time properties
(gw_setup_window): kill (replaced by constr. time props)
(gpdf_window_construct): don't call gw_setup_window
(gw_add_control_to_ui, gpdf_window_open): more simplifications due
to BonoboWidget
(gw_activate_control): ditto -> kill
(gw_control_load_pdf, bonobo_stream_for_uri): extract the latter
from the former
(gw_setup_local_contents, gw_setup_toplevel_ui)
(gw_setup_recent_menu, gw_setup_recent_toolitem): slot and
ui_component moved to priv

* shell/gpdf-window.h (struct _GPdfWindow): move away remaining public
fields