cleanup code
fix a memleak in dc_widget
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