libdivsufsort should use int_vector<>

[mpetri]

now that libdivsufsort is included in the library it would be very nice to modify it to use the sdsl int vector to enable bit compression among other things.

[simongog]

Yes, we can modify that. I will also extend the memory management system in such a way that single int_vectors can be mapped to hugepages and we therefore gain time in the construction process.