Add SQLite dep to hack/PACKAGERS.md

Copied from IRC:
> latest sqlite stable is 3.8.1, latest Gentoo stable is 3.7.17, wheezy is at 3.7.13, precise is at 3.7.9
> f18 is at 3.7.13, f19/f20 are at 3.8.0

Thus for now, 3.7.9 is the lowest common denominator unless someone speaks up now to tell us otherwise. :)