[C/C++ PATCH] -Wunused-but-set-variable fixes (PR c++/44361)

[Jason Merrill]

On 06/01/2010 05:26 PM, Jakub Jelinek wrote:
> +  if (implicit == NULL)
> +    mark_rvalue_use (expr);

An explicit cast to void still isn't using it as an rvalue; this should 
be mark_exp_read.  The C++ hunk is OK with that change.

Jason