Power PC long double repr needs more precision.

On PPC this test fails as reported in #7836

```
    o = 1 + np.finfo(np.longdouble).eps
    assert_equal(np.longdouble(repr(o)), o,
                 "repr was %s" % repr(o))
```

with

```

AssertionError:
Items are not equal: repr was 1.0
 ACTUAL: 1.0
 DESIRED: 1.0
```

Among other things, probably finfo, it looks like repr does not have sufficient digits.
