edit: fix bug when there is no line under current cursor
listctrl: fix left/right key handling

Thanks haitao for the bug report.
listctrl: preserve the current_item in rtgui_listctrl_set_items
window: record the outer clip

If we don't record the outer clip, call rtgui_win_update_clip more than
once will clip out all the widgets.

Thanks the bug report from haitao.
window: fix a memleak
window: don't update the clip of closed window
topwin: code cleanup
window: fix bug that the window title not updated in some cases

In some cases, there is no PAINT event follow the ACTIVATE event, so
always update the title.

Thanks haitao for the bug report.
dc_blend: fix the negative clip in rtgui_dc_blend_point
rtgui_system: the win_create event does not have extent