explorer: graphical leaks in SDI mode

The toolbar in SDI mode is not resized properly (tested on Windows XP and Windows 2000). Also, there is a one-pixel line between the toolbar and the two panes that is not redrawn (so pixels that were already there before ex. a task switch are not erased). Plus there is a one-pixel vertical line of pixels between the two edit boxes that is not erased/redrawn. See attached screenshot.