Legend labels order

[Marco Caliari]

Dear maintainers,

I discovered the following problem in 3.2.x. When you have two plots but 
only one legend label, such as in

x=linspace(0,10);,plot(x,x,x,x.^2),legend('linear')

the label is attached to the second plot. Similar behavior in the case

x=linspace(0,10);,plot(x,x,x,x.^2,x,x.^3),legend('linear','quadratic')

or

x=linspace(0,10);,plot(x,x),hold on,plot(x,x.^2,'g'),legend('linear')

I'm able to fix this problem if I substitute

set (kids(k), "keylabel", arg);

with

set (kids(nkids-nargs+k), "keylabel", arg);

in legend.m (two occourences). But, since there is a similar code some 
rows above regarding hggroup (and I don't know what a hggroup is), I 
cannot submit a complete patch. I hope somebody else can fix it.

Best regards,

Marco