[raw-string] indentation stripping

[Jim Laskey]

> 
> P.S. We can actually have it both ways: do the stripping if and only if the number of tick marks is even.  :-b
> 
>   String myNestedExample = ````
>     String seven = ``
>         +-----------------+
>         | a nice neat box |
>         +-----------------+
>         ``;
>   ````;

Groan