Support large files and fix an initialization problem

[joshuaehill]

• Add support for datasets with large number of samples files. (> 2GS).
  • Requires divsufsort64 (generally included in the relevant package).
• Resolved initialization error in ea_conditioning.

[joshuaehill]

This is mainly useful because it allows for more samples of wide data; this comes up most frequently with the bitstring tests. For 8-bit data, the prior code would fail when the dataset was larger than about 256MB.

[celic]

The changes look fine but we need to do some testing with this to ensure that including the new -ldivsufsort64 library doesn't affect our ESVTS build process. Are both libraries needed? Or can we remove the -ldivsufsort now?

[joshuaehill]

Both libraries are required when linking. The tool opportunistically uses the 32-bit-index version of the tool when it can, because the 32-bit-index version of the library uses literally half the memory of the 64-bit-index version.

[celic]

The math checks out on that one. I'll test this out on an internal ESV environment to ensure it doesn't break anything before I merge it in.