Log Message:
Update gtk3 to 3.20.8

Overview of Changes in GTK+ 3.20.8
==================================

* Revert an unintentional bump of the GLib requirement in 3.20.7

Overview of Changes in GTK+ 3.20.7
==================================

* Bugs fixed:
 118959 GtkScale value '-0'
 674215 regression with updating tooltips
 708148 gtk_tree_view_get_path_at_pos mistakenly identifies column of ini...
 745622 Selected text not highlighted in GtkInfoBar
 747206 gtktextview: note on how to get line spacing between two paragraphs
 764060 opening a second nautilus while a delete operation is in progress...
 764203 Default background color for the 'textview border' node
 765924 Improve external drives detection
 766120 Scale draw_value() align changed from centre/right (H/V) to lefti...
 766122 Re-used filechooser displays $pwd half of the time when shown
 766341 Do not rely on memfd as it requires a fairly recent kernel
 766643 Frozen windows when unmapped with pending configure event
 766782 OpenGL in broadway leads to segmentation fault
 767058 GtkInfoBar: right-click/context menu all white
 767468 Popover over a treeview cellrenderer is hidden immediately after ...
 767705 GtkActionHelper: Change a message to a warning
 767766 CUPS 2.X detected incorrectly by configure
 767795  Warning when the "accelerator" property of \ 
GtkShortcutsShortcut ...
 767848 crash in the window test
 767851 Adwaita: popover arrows broken in some orientations
 768016 [Wayland] Submenus often get closed after ~2 seconds
 768025 entry.warning & entry.error broken
 768082 wayland: copying from Wayland to NEdit (Xwayland/Motif) doesn't work
 768142 Incorrect order of $(LIBS) and $(OBJS) in Makefile.example caused...
 768177 CLIPBOARD target request after PRIMARY request times out. GDK_SEL...
 768485 Change the priority of the window-close idle to G_PRIORITY_DEFAULT
 768657 places-view: fix open action for locations without a mount or volume
 768930 reftests: override GSETTINGS_SCHEMA_DIR when running tests
 769003 Adwaita: GtkCalendar uses a confusing style for week of year
 769047 GtkWidget <-> GtkStyleContext API not clear

* Translation updates:
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