perf/core improvements and fixes:

User visible:

- Allow reading from a backward ring buffer (one setup via sys_perf_event_open
  with perf_event_attr.write_backward = 1) (Wang Nan)

Infrastructure:

- Fix the build on Android NDK r12b (initially just for arm), that is now port
  of my perf-build container collection and will get tested prior to sending
  patches upstream (Arnaldo Carvalho de Melo)

- Add correct header for ipv6 defini

- Fix bitsperlong.h fallout (Arnaldo Carvalho de Melo, Peter Zijlstra)

- Use base 0 (auto) in filename__read_ull, so that we can handle hex values too (Jiri Olsa)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2
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=QHDr
-----END PGP SIGNATURE-----