See https://github.com/zopefoundation/zope.interface/pull/202#pullrequestreview-389126705

Cooperate with InterfaceClass to ensure there is no performance penalty for this. Fixes #3

+-------------------------------------------------------------+----------------+------------------------------+------------------------------+
| Benchmark                                                   | bench_master38 | bench_issue3                 | bench_issue3_opt             |
+=============================================================+================+==============================+==============================+
| call interface (provides; deep)                             | 369 ns         | 454 ns: 1.23x slower (+23%)  | not significant              |
+-------------------------------------------------------------+----------------+------------------------------+------------------------------+
| call interface (provides; wide)                             | 373 ns         | 457 ns: 1.22x slower (+22%)  | 365 ns: 1.02x faster (-2%)   |
+-------------------------------------------------------------+----------------+------------------------------+------------------------------+
| call interface (no alternate, no conform, not provided)     | 671 ns         | 760 ns: 1.13x slower (+13%)  | 636 ns: 1.06x faster (-5%)   |
+-------------------------------------------------------------+----------------+------------------------------+------------------------------+
| call interface (alternate, no conform, not provided)        | 395 ns         | 494 ns: 1.25x slower (+25%)  | not significant              |
+-------------------------------------------------------------+----------------+------------------------------+------------------------------+
| call interface (no alternate, valid conform, not provided)  | 250 ns         | not significant              | 227 ns: 1.10x faster (-9%)   |
+-------------------------------------------------------------+----------------+------------------------------+------------------------------+
| call interface (alternate, invalid conform, not provided)   | 348 ns         | 424 ns: 1.22x slower (+22%)  | not significant              |
+-------------------------------------------------------------+----------------+------------------------------+------------------------------+

Fixes #192 and fixes #194.

Also fix the IRO for OrderedDict on CPython 2

None of the elegant solutions mentioned in the issue worked out, so I had to brute force it.

Fixes #8

Fixes #21

The 'mostly' is because interfaces are used in cases that C3 forbids;
when there's a conflict, we fallback to the legacy algorithm. It turns
out there are few conflicts (13K out of 149K total orderings in Plone).

I hoped the fix for #8 might shake out automatically, but it didn't.

Optimize the extremely common case of a __bases__ of length one.

In the benchmark, 4/5 of the interfaces and related objects have a base of length one.

Fix the bad IROs in the bundled ABC interfaces, and implement a way to get warnings or errors.

In running plone/buildout.coredev and tracking the RO requests, the
stats for equal, not equal, and inconsistent-so-fallback, I got
{'ros': 148868, 'eq': 138461, 'ne': 10407, 'inconsistent': 12934}

Add the interface module to the Attribute str.

This was extremely helpful tracking down the Plone problem; IDate is defined in multiple modules.