gdk/win32: Fix build after GdkScreen and settings changes

gdk/win32: Fix build after GdkScreen and settings changes

Implement GdkDisplay->get_setting() using the existing
_gdk_win32_screen_get_setting() and get rid of GdkScreen->get_setting()
as a result, to follow the changes in GDK.

Also, since we don't emit settings events in the Windows GDK backend,
but we acquire settings to print using GDK_SETTING, drop all references
related to GDK_SETTING since that is now removed.  Update the debug
strings that are print out as a result
(gdk_screen_get_setting->gdk_display_get_setting).

https://bugzilla.gnome.org/show_bug.cgi?id=773299