increasing disparity search range to 512

[raghavkhanna]

This would enable higher resolution images to be used, perhaps increasing precision/accuracy.
Any pointers on how to go about it would be much appreciated! Thank you.

[cagbal]

The same request here. Appreciate it if we can use other values (generally higher) for disparity than 64, 128, 256.

[Sir-Photch]

I implemented 512 disparity support on a branch of my fork: https://github.com/Sir-Photch/libSGM/tree/512-support

It seems to work properly, that is: the disparity images look fine. However, I had to make multiple changes to bit-widths of computations in the CUDA code and I cannot verify the correctness for it (yet?). The original test suite sgm-test works fine though.

If the maintainers of this project are interested, I'll gladly submit a PR.