[RFA] Remove a cleanup from parse_expression_for_completion

[Simon Marchi]

On 2018-02-16 18:02, Tom Tromey wrote:
> This removes a cleanup from parse_expression_for_completion, by
> changing various expression-completion functions to use std::string
> rather than explicit malloc+free.

That looks good to me.  You can go a bit further if you want and make 
add_struct_fields take a const std::string reference as well.

Simon