perf record: Use ring buffer consume method to look like other tools

All builtins that consume events from perf's ring buffer now end up
calling perf_evlist__mmap_consume(), which will allow unmapping the ring
buffer when all the fds gets closed and all events in the buffer
consumed.

This is in preparation for the patchkit that will notice POLLHUP on
perf events file descriptors.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-8vhaeeoq11ppz0713el4xcps@git.kernel.org


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