Log Message:
Update gtk3 to 3.20.3

Overview of Changes in GTK+ 3.20.3
==================================

* Bugs fixed:
 764174 Configuration dialog is too small
 764203 Default background color for the 'textview border' node
 764204 Primary and secondary carets/cursors not distinguishable by default
 764261 gtkplacesviewrow: untranslated "%s / %s available"
 764374 Busy loop while "Displays" page is active
 764378 gtk3-demo won't run without hicolor-icon-theme
 764540 gtk_scrollable_get_border is missing annotations
 764585 Fix "format not a string literal" errors
 764686 build failure after "make distclean"
 764710 GtkListBox row CSS nodes do not reflect visual order
 764835 broadway: fix documentation, correct display port details
 764664 Segfault when initializing WINTAB pressure-sensitive tablets

* Translation updates:
 Bulgarian
 Esperanto
 Greek
 Persian