perf record: Implement control commands handling

perf record: Implement control commands handling

Implement handling of 'enable' and 'disable' control commands coming
from control file descriptor.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/f0fde590-1320-dca1-39ff-da3322704d3b@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>