[PATCH] [PR gdb/16238] Add completer for the show user command

[Lancelot SIX]

> 
> Add curly braces for the outer "if", and the "for" doesn't need them.
> 
> Otherwise, this is OK, thanks.
> 
> Simon

Hi,

Thanks for the review.

I have fixed the code according to your remark and pushed this commit.

Best,
Lancelot.