[Bug c/66425] (void) cast doesn't suppress __attribute__((warn_unused_result))

[rusty at rustcorp dot com.au]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425

--- Comment #3 from rusty at rustcorp dot com.au ---
Indeed, cast to void has been a standard "I really want to ignore this"
notation.  It's intuitive and obvious, and ISTR seeing it in the early 90s for
lint warning suppression, for example.