y axisScaling for multiple line plot

[Johann Krauter]

if a 2D dataObject is plotted as a 1D plot (for each x-axis data a line plot), the scaling of the y axis is calculated only by the of the first line plot. Maybe it is connected with commit #eba1c0d?

[M. Gronle]

itom1dqwtplot: fixes issue #23: auto scaling always considers all displayed curves, some more code refactoring and memory leak fix.

→ <<cset 9f8302ff6289>>