Functions for loading inet.data entities from flat line-oriented files.

Functions for interfacing with Mozilla Public Suffix List format files.

The supported format is an extended version of the PSL format.  There are two
differences:

 - Lines beginning with `#` are considered to be comments in addition to lines
   beginning with `//`.

 - Supports a new "dynamic" rule type, indicated by prefixing a domain with a
   `+` character.  Dynamic rules act as per normal rules, unless the lookup
   domain is identical to the suffix domain.  In that that case, the lookup
   falls through to the next matching rule instead of terminating with a null
   result.

See the tests for examples.