Reverted wheel action in 1.0.4pre6

[Günther]

The wheel action should be:

Scoll down in the text if the wheel is turned 'down', i.e. clockwise if
you see the mouse from the left side.
This is at least a convention used in all word processors I have seen.

Now it is just the opposite, at least on linux (RH6, XFree 3.3.1).
If the outcome is different on different OSs a wheel scroll direction
variable
should be introduced.  I have just chaned the wheel direction in
BufferView.C back to what it used to be.

Ulrich