Syncing libtatum with VTR

[AlexandreSinger]

libtatum in VTR and this repository have diverged over the past 4 years. Pushing back the VTR changes that currently are not in this repo.

I used git subtree push in order to keep the authors of the commits the same.

I was able to build tatum in serial mode, but the reg_test script does not seem to work; so I cannot verify if tatum works out of tree, but it obviously works in VTR.