gdk3 rbgdkdevice.c: implement Gdk::Device#get_window_at_position and
Gdk::Device#get_device_position'
gdk3: implement Gdk::Device#ungrab
gdk3: implement Gdk::Display#device_is_grabbed?
gdk3: add rbgdkdevicemanager.c
gdk3: remove trailing spaces
gdk3: add Init_gdk_device_manager() default declaration
gdk3: add declaration Init_gdk_device_manager
gdk3: add macro to treat GDK object
gdk3: implement Gdk::Device#get_position and Gdk::Device#warp Gdk::Device#grab
gdk3: implement Gdk::Window#get_device_position
gdk3: add deprecation methods to deprecated.rb
gdk3: use GOBJGLIST2RVAL_FREE() instead
gdk3: remove unneeded implement API
gdk3: remove trailing spaces
gdk3: remove obsolete API
gtk3: remove obsolete API
gtk3: remove trailing spaces
gtk3: add deprecation methods to deprecated.rb
gdk3: improve Gdk::Device#ungrab API
gdk3: avoid needless C -> Ruby type conversion