Export rtgui_container_get_object function.
Merge branch 'master' of https://github.com/RT-Thread/RTGUI
Add window buffer DC.
Change DC win to DC widget.
Rename DC win to DC widget
Add the offset (x, y) in the DC widget. Add DC buffer in the window.
cleanup code
fix a memleak in dc_widget
Add the DC buffer for window.
implement the buffered window dc
dc_buffer: fill_rect should use background color
Merge branch 'animation' of https://github.com/grissiom/RTGUI into grissiom-animation

Conflicts:
	components/rtgui/common/dc_client.c
	components/rtgui/include/rtgui/widgets/window.h
Add VFB.
Remove DC widget.
Remove DC widget
Fix clip region issue in the rtgui_win_get_drawing routine.
Add VPAINT in the event dump.
Add screen_lock_freeze/thaw routine.
Use rtgui_dc_get_visible function to instead of RTGUI_WIDGET_IS_DC_VISIBLE.
Add VPAINT_REQ handle in the RTGUI application.