Fix two bugs in SetScrollRange

[Troy Rollo]

This fixes two bugs in SetScrollRange:

1. Setting the scroll range with the "bRedraw" flag set to true on a 
non-control scrollbar results in the scrollbar being drawn over the whole 
window area.

2. If you don't set WS_HSCROLL/WS_VSCROLL on window creation, setting a scroll 
range does nothing. Setting the scroll range to a non-zero range should cause 
scroll bars to be displayed (and the appropriate flag to be set in the window 
styles). Setting the range to a zero range should cause the relevant scroll 
bar to be hidden (and the flag to be removed from the window styles).

The second attachment is a test program that can be used to verify the 
behaviour associated with the second bug by using the left and right mouse 
buttons to set a non-zero/zero scroll range on mouse-down/mouse-up. The left 
mouse button affects SB_HORZ and the right affects SB_VERT.
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