capture: keep all output for "Captured stdout call" etc

[blueyed]

It looks like using capfd.readouterr() in a test also resets what pytest displays in case of failed tests.

For this I think it would be useful to keep the output in total.

capfd = <_pytest.capture.CaptureFixture object at 0x7fc6da051908>

    def test_capfd(capfd):
        print('stdout')
        print(2, capfd.readouterr())
        print(3)
>       assert 0
E       assert 0

tests/test_capfd.py:11: AssertionError
----------------------------------- Captured stdout call ------------------------------------
2 CaptureResult(out='stdout\n', err='')
3

Here the stdout is missing.

pytest master (08aed1a).