addUnexpectedSuccess and addExpectedFailure error out when used with trial

[Jonathan Lange]

You can't reliably use testtools TestCases with trial, because Trial's reporter is incompatible with modern `addUnexpectedSuccess` and `addExpectedFailure` protocols

Trial's `IReporter` interface has the following:

```
    def addUnexpectedSuccess(test, todo):
    def addExpectedFailure(test, error, todo):
```

Where `todo` is a `Todo` object, and there are notes saying that it should just be a string.

testtools's result interface has:

```
    def addUnexpectedSuccess(test, details=None):
    def addExpectedFailure(test, err=None, details=None):
```

(edited for notation compatibility)

And when testtools wraps other results with ExtendedToOriginalDecorator, it anticipates the following signatures:

```
    # unexpected success
    def addUnexpectedSuccess(test, details):
    def addUnexpectedSuccess(test):
    def addFailure(test, err)

    # expected failure
    def addExpectedFailure(test, details):
    def addExpectedFailure(test, err):
    def addSuccess(test):
```

This is a plain messy compatibility issue. While it's not strictly a bug in testtools, testtools might well be the most effective place to fix it. There's precedent, in that we already have backwards compatibility code for legacy TestResults.

[Jonathan Lange (jml)]

Fixed in Twisted