Changes

NEWT.Window: Refine string representation, renamed append(StringBuilder) -> toString(..), added toSimpleString(..)

This also revised commit f56adf14deadd4ee8f434ea1293e27bcafdf2a90 Window API addition of 'append(StringBuilder)',
which has been renamed to 'toString(StringBuilder)' as aligned to out other classes.

Bug 1422: Use own deviceZoomScaleUp(..) disregarding higher-toolkit's compensation like 'DPIUtil.useCairoAutoScale()'

We can't use DPIUtil's 'autoScaleUp(..)' method on non-native DPI scaling platforms
as it uses a scale-factor of 1f if the higher toolkit compensates, i.e. 'DPIUtil.useCairoAutoScale()'.

Since NEWT uses X11 and GDI directly, which are not DPI scale-aware,
we have to drop the semnatics of 'DPIUtil.useCairoAutoScale()'
and merely use the actual 'deviceZoom'.

This was proposed by Marcel Au in the first place.
At least I understand these semantics by now.

+++

Additionally NewtCanvasSWT.SWTNativeWindow needs to return the 'deviceZoomScaleUp(..)'
values for returning its size in window- and pixel-units (surface).