Debug printfs around --date timestamp implementation.
Fix compiler warning and add a comment.
Remove unused -C command arg which was causing compiler warning.
Fix compiler warning and remove a line of deadc0de.
Debug printf.
Make reads nonblocking when getting timestamp for record --date option.

On my machine, trace-cmd record --date just hangs, as the STAMP message written
to trace_marker only ends up on one CPU.  The first read() on a per-cpu raw
trace pipe just blocks.