perf beauty: Add CLEAR_SIGHAND support for clone's flags arg

Add support for the recently added CLONE_CLEAR_SIGHAND flag.

This takes advantage of the copy of the uapi/linux/sched.h we have in
tools/include, which allows us to build tools/perf in older systems and
have the binary support printing that flag whenever that system gets its
kernel updated to one where this feature is present.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Adrian Reber <areber@redhat.com>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org
Link: https://lkml.kernel.org/n/tip-1vnz497ubtu5oz16ygdcul0e@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>