itimerval can contain padding that may be legitimately uninitialized.
On NetBSD there are four integers of type "long, int, long, int", the
int argument stands for __sanitizer_suseconds_t. Compiler adds extra
padding in this layout.
Check every field of struct itimerval separately.
Define sanitizer_suseconds_t as long on FreeBSD, Linux and SmartOS,
and int on NetBSD. Define sanitizer_timeval and __sanitizer_itimerval.
Sponsored by <The NetBSD Foundation>