perf script: Set reference time if file is a pipe

Allows time-of-day timestamps when events are directed from perf-record
to perf-script through a pipe. e.g.,,
    perf record -e <list> -D | perf script

Signed-off-by: David Ahern <dsahern@gmail.com>
tools lib traceevent: Add support for pIS address format

Signed-off-by: David Ahern <dsahern@gmail.com>