Rounding the axes dimensions to "nice" number may have been a
good idea, but for the time-axis it feels weird.
Therefore revert the time axis to the previous behavior:
range is set according to the data. To differentiate between
time an other axes, use the position: the time axis is the
only axis at the bottom. Yes, that's ugly but pragmatic.
Since we have that flag also use it for the special casing
of the text-display. Spares us one virtual function dispatch.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
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