New example added

[Uwe R. <Uwe...@mu...>]

Hi,

I added a new example 'realtime_plot' to the CVS tree. It shows how to implement
dynamicly growing curves and contains an implemetation of stacked zooming using
scrollbars.

The code needs more comments and some polishing, but the important stuff is
working.
Hope I can continue soon. 

I didn't change examples.pro, so tmake must be done in realtime_plot by hand.
The .pro file doesn't set the necessairy paths for includes and lib like all
examples. Did I miss the idea behind this ?

I have no environment beside linux running, so maybe someone could check it
on the Win platforms. I use the random() call, don't know if it is available
there.
---

Another bug I noticed is that QwtPlot doesn't paint the axis scales and the grid
if there is no curve with at least one point. The reason is because QwtPlot
doesn't know how to autoscale if there is no data, but in case of fixed scaling
it could be done easily. Should I add a fix, when the 0.2i is done ?

Uwe