[eigen] checking for NaN

["Radu B. Rusu" <rusu@xxxxxxxxxxxxxxxx>]

I was wondering if there's a need for optimized versions for isNaN, isFinite, etc. I caught Benoit talking about it
earlier last year (http://forum.kde.org/viewtopic.php?f=74&t=96166), and did a bit of searching  online to find
discussions here: http://locklessinc.com/articles/classifying_floats/ and here:
https://bugzilla.mozilla.org/show_bug.cgi?id=416287

Due to the nature of our data, we end up calling isNaN extensively on large datasets, and we end up running things like:

return (pcl_isfinite (p.x) && pcl_isfinite (p.y) && pcl_isfinite (p.z));


The article from locklessinc seemed interesting with respect to an optimized SSE version for Vector4f.

Thanks,
Radu.