use OpenLayers.Control.DrawFeature to work around onselectstart mixup in IE

fix #855
use OpenLayers.Control.DrawFeature instead of OpenLayers.Control.DynamicMeasure when drawing box or circle to work around an event mixup with document.onselectstart between DynamicMeasure and OL Drag handler in IE
well, I guess I could use a non-translated variables, but then half of the code would use non-translated variables and the other half translated variables.
the point here is not to make that code nice but have something working, and by using translated variables at least it stays globally coherent with the non-modified code
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