recognize Sympy's NonElementaryIntegral

<div id="comment:0"></div>

We don't translate a Sympy result properly:

```
sage: integral(log(x)/(x^2 - 1),x,0,infinity, algorithm='sympy')
...
AttributeError: 'NonElementaryIntegral' object has no attribute '_sage_'
```
This should likely be done upstream, as previously.

CC:  @kcrisman

Component: **calculus**

_Issue created by migration from https://trac.sagemath.org/ticket/17935_

