Reduce vertex density in PDF output to match device resoution

[ajr@…]

Currently the PDF output includes a vertex for every single vertex that exists 
in the input arc. For large input layers, this results in PDF outputs that are 
needlessly large as they often have thousands of vertices per inch, whilst most 
printers still only do 600 dpi.

It would be nice if the PDF renderer did the same thing I saw (somewhere) 
inside Mapserver, where vertices are discarded as they are read, unless they 
are over the pixel boundary. This is an ugly generalization algorithm, but 
reasonably fast and the effects are not overly noticable in screen output.

Perhaps SIZE and/or IMGSIZE could also influence vertex thinning so that the 
output vertex density is comparable to output resolution?

> I think this would be a good thing to do and you should probably write a 
> bug on it so the idea does not get lost.
>
> -Steve W.

[assefa]

Not dealing with this for 4.4 release.