[Rd] Legend frame error (PR#9236)

[tgibson at augustcouncil.com]

Hello,
The frame drawn around the legend appears to miscalculate when the
x-axis decreases rather than increases.  Pasted below is a simple
testcase.  When the x-axis decreases, the width of the legend frame
appears to be calculated based on the length of the first item, rather
than the maximum length of all items.

Thanks,
-TAG
Todd A. Gibson

line1=dpois(seq(0,50), 10)

par(mfcol=c(2,1))

plot(line1, col="blue", type="l")
legend(x=30,y=0.10, legend=c("binding","transcription","Random Genes"), col=c("red", "blue","black"),lty=c(1,1,2),lwd=c(2,2,1))

plot(line1, col="blue", type="l", xlim=c(50,0))
legend(x=30,y=0.10, legend=c("binding","transcription","Random Genes"), col=c("red", "blue","black"),lty=c(1,1,2),lwd=c(2,2,1))