Distance bits

[xchang1]

This adds a field to the temporary distance index to count the number of bits needed per entry in the final distance index vector.

[adamnovak]

We might need adamnovak/libdivsufsort@24f3c42 in the libdivsufsort in our sdsl-lite, if we go into sdsl-lite through CMake and not install.sh.

[xchang1]

Ok, I updated the submodules to use newer cmake versions. sdsl-lite now uses @adamnovak's libdivsufsort. This is maybe not great but the version we were using before (https://github.com/simongog/libdivsufsort) was last updated 9 years ago, and what looks like the original (https://github.com/y-256/libdivsufsort) was updated 10 years ago.

@adamnovak I also noticed that the pybind11 submodule comes from pybind, but CMake is getting it from RosettaCommons. I think the submodule is not actually used but I'm not sure.