Updates for compiling with Gtk+ 3.0 (--with-x-toolkit=gtk3).

Updates for compiling with Gtk+ 3.0 (--with-x-toolkit=gtk3).

* configure.in: Require 3.0 for --with-gtk3.  Add HAVE_GTK3.

* doc/emacs/xresources.texi (GTK resources): ~/.emacs.d/gtkrc does not work
for Gtk+ 3.

* src/gtkutil.c: Include gtkx.h if HAVE_GTK3.  If ! HAVE_GTK3, define
gdk_window_get_screen, gdk_window_get_geometry,
gdk_x11_window_lookup_for_display and GDK_KEY_g.
(xg_set_screen): Use DEFAULT_GDK_DISPLAY.
(xg_get_pixbuf_from_pixmap): New function.
(xg_get_pixbuf_from_pix_and_mask): Change parameters from GdkPixmap
to Pixmap, take frame as parameter, remove GdkColormap parameter.
Call xg_get_pixbuf_from_pixmap instead of
gdk_pixbuf_get_from_drawable.
(xg_get_image_for_pixmap): Do not make GdkPixmaps, call
xg_get_pixbuf_from_pix_and_mask with Pixmap parameters instead.
(xg_check_special_colors): Use GtkStyleContext and its functions
for HAVE_GTK3.
(xg_prepare_tooltip, xg_hide_tooltip): Call gdk_window_get_screen.
(xg_prepare_tooltip, create_dialog, menubar_map_cb)
(xg_update_frame_menubar, xg_tool_bar_detach_callback)
(xg_tool_bar_attach_callback, xg_update_tool_bar_sizes): Call
gtk_widget_get_preferred_size.
(xg_frame_resized): gdk_window_get_geometry only takes 5
parameters.
(xg_win_to_widget, xg_event_is_for_menubar): Call
gdk_x11_window_lookup_for_display.
(xg_set_widget_bg): New function.
(delete_cb): New function.
(xg_create_frame_widgets): connect delete-event to delete_cb.
Call xg_set_widget_bg.  Only set backgrund pixmap for ! HAVE_GTK3
(xg_set_background_color): Call xg_set_widget_bg.
(xg_set_frame_icon): Call xg_get_pixbuf_from_pix_and_mask.
(xg_create_scroll_bar): vadj is a GtkAdjustment for HAVE_GTK3.
Only call gtk_range_set_update_policy if ! HAVE_GTK3.
(xg_make_tool_item): Only connect xg_tool_bar_item_expose_callback
if ! HAVE_GTK3.
(update_frame_tool_bar): Call gtk_widget_hide.
(xg_initialize): Use GDK_KEY_g.

* src/xmenu.c (menu_position_func): Call gtk_widget_get_preferred_size.

* src/xsmfns.c (gdk_set_sm_client_id): Define to gdk_set_sm_client_id
if ! HAVE_GTK3
(x_session_initialize): Call gdk_x11_set_sm_client_id.

* src/xterm.c (XFillRectangle): Use cairo routines for HAVE_GTK3.
(x_term_init): Disable Xinput(2) with GDK_CORE_DEVICE_EVENTS.
Load ~/emacs.d/gtkrc only for ! HAVE_GTK3.

* src/xterm.h (DEFAULT_GDK_DISPLAY): New define.
(GDK_WINDOW_XID, gtk_widget_get_preferred_size): New defines
for ! HAVE_GTK3.
(GTK_WIDGET_TO_X_WIN): Use GDK_WINDOW_XID.