To aid in catching bugs when using atomics as a reference count.

This is a trimmed down version with just what is used by tools/ at
this point.

After this, the patches submitted by Elena for tools/ doing the
conversion from atomic_ to recount_ methods can be applied and tested.

To activate it, buint perf with:

  make DEBUG=1 -C tools/perf

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Elena Reshetova <elena.reshetova@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-dqtxsumns9ov0l9r5x398f19@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>