[R-SIG-Mac] Minor bug in Quartz sizing

[Duncan Murdoch]

With a current R-patched (2.13.1 Patched (2011-09-02 r56906)), the 
following code generates plots missing the bottom labels:

par(mfrow = c(4, 5), mar = c(2.1, 2.1, 4.1, 1.1))
for (i in 1:20) plot(1)

If I resize the plot at all, it's redrawn correctly, with all margins 
showing.  After resizing, repetitions in the old window are fine, but if 
I close it and try again, the error re-surfaces.

I'm on Mac OSX 10.6.8.

Duncan Murdoch