patch to scale label buffers and offsets for printing

[mhugent]

The following patch adds scaling of label buffers and offsets for printing. Additionally, the font is requested in a larger size and the painter is downscaled to have a better font appearance when printing (to avoid the so-called Qt font scale bug). Finally, the buffer size is considered in the label size calculation.

Martin, could you review this patch (just to avoid I'm breaking something in the new labeling engine)? But no hurry, I know you are very busy these days.

Marco

[mhugent]

new patch version does not use 1mm margin and does not consider buffer size for curved line labels (gives better prints for curved labels compared to first patch)

[wonder]

Applied in r13599.

I've simplified the calculations of positions as it was starting to be hairy. I think the buffer size shouldn't be considered for the labels as it complicates things and actually it might be desirable to allow the buffers of neighboring labels to coalesce. But we could add a "margin" property, which would allow the user to set properly the minimum distance from other labels.