bug#344: plot not cleared after plot() commands following a plotyy()

[Thomas Weber]

thanks
[let's give the tracker a try]

[ Octave 3.0.1, gnuplot 4.2 patchlevel 2 ]

The following code leaves fragments of the plotyy() commands in the
final plot after the plot() command:

===================================================================
x= 1:10;
y = 1./x;
z = 10 *x;
q = 100*x;

plotyy(x,y,x,z)
pause
plotyy(x,y,x,q)
pause
plot(x,y)
===================================================================

        Thomas