Improved variant of patch to plot() (fwd)

[Ilya Zakharevich <ilya@math.ohio-state.edu>]

I wrote
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 When inspecting the output of plot(), I found that the output of the
 labels was completely screwed up, which an addition to visual clutter
 misplaces data points where function takes the minimal values.

 Here is the improved variant of the previous patch which puts the
 label in "%g" format, and in correct places.
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Sorry, I screwed %g format in my previous message.  It should be
something like %8.7g, but not exactly, since this is too long on big
numbers. 

Please ignore this patch until I get more fluence with formats.

Ilya