triple quote and %s at beginning of line with %paste

Hi!

This is very similar to the already fixed problem here:
https://github.com/ipython/ipython/issues/558

But the problem persists if the magic function %paste is used.

So if you copy & paste the following in ipython

```
print """
%s
"""
```

you get 

```

%s

```

as output, but if you use `%paste -q` instead of normal pasting, you get

```

get_ipython().magic(u's ')

```
