legend vs. hggroup

[John W. Eaton]

While debugging the axis problem with fplot, I noticed that the call
to legend in fplot is also failing.  I think the problem is that the
plot function now creates an hggroup object, but legend is expecting
to label lines.  I'm not sure of the right way to fix this problem.
Should legend be modified to also look for hggroup objects?  For the
gnuplot backend, do we need to add the keylabel property to the
hggroup object?

jwe