[C++ Patch] Use declarator->id_loc in three additional places

[Jason Merrill]

On 6/4/19 10:31 AM, Paolo Carlini wrote:
> +	      permerror (loc, "member functions are implicitly "
> +			 "friends of their class");

Wouldn't it be better to use the location of "friend" in this diagnostic?

The rest of the patch is OK.

Jason