hold for limit

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

A hold for limit could be useful for things like typesetting - see http://stackoverflow.com/questions/32552515/sage-notebook-limit-representation

```
sage: limit(x^2, x=0, hold=True)
sage: latex(limit(x^2, x=0, hold=True))
```

CC:  @paulmasson

Component: **symbolics**

_Issue created by migration from https://trac.sagemath.org/ticket/19203_

