demo: encode mywidget.h as cp936

VC does not recognize UTF-8, sign...
Add rtgui_dc_get_pixel_format function for DC; Fix JPG/PNG image issue;
demo: port to new type structure
widget: notebook: record the focus widget and restore it on switching back
widget: fix the parent type of checkbox
Use ellipse routine for circle drawing; Add AA circle/ellipse drawing routine.
Fix the image of iconbox NULL issue.
Add lodepng decoder.
Fix lodepng compiling issue.
remove components that in the main RT-Thread repo