Riegl Extra Bytes support.

Hi,
Yesterday I posted in the mailing list about the support for Riegl clouds.
I'm in a hurry so I came up with this dirty hacky solution for reading LAS files with the extra bytes.

With the original code, the Riegl cloud was all messed up, when visualizing it the road that was mapped transformed into this:

![bad_riegl](https://cloud.githubusercontent.com/assets/2392791/3055207/139e307e-e1bf-11e3-8b1a-20c492ed62b5.png)

That same LAS was percectly visualized using Qt Reader. With my hacky temp solution, I was able to visualize the cloud without problems:

![good_riegl](https://cloud.githubusercontent.com/assets/2392791/3055279/b20d2170-e1bf-11e3-8edf-c7c46d6fef44.png)

I'm pulling this up so others may use the hack to work with Riegl clouds until an official solution comes up. :)