perf tool: Make perf tool aware of SELinux access control

Implement selinux sysfs check to see the system is in enforcing mode and
print warning message with pointer to check audit logs.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-security-module@vger.kernel.org
Cc: selinux@vger.kernel.org
Link: http://lore.kernel.org/lkml/819338ce-d160-4a2f-f1aa-d756a2e7c6fc@linux.intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>