Functions to load inet.data entities from flat, line-oriented files.

Functions to use Mozilla Public Suffix List format files.

The supported format extends the PSL format. It has these differences:

- Lines that begin with `#` are comments. Lines that begin with `//` are also
  comments.

- A `+` before a domain indicates a "dynamic" rule. Dynamic rules act as
  normal rules unless the lookup domain is identical to the suffix domain. In
  this case, the lookup continues with the next matching rule.

See the tests for examples.