Allow use of hashmap in perf. Modify perf's check-headers.sh script to
check that the files are kept in sync, in the same way kernel headers
are checked. This will warn if they are out of sync at the start of a
perf build.

Committer note:

This starts out of synch as a fix went thru the bpf tree, namely the one
removing the needless libbpf_internal.h include in hashmap.h.

There is also another change related to __WORDSIZE, that as is in
tools/lib/bpf/hashmap.h causes the tools/perf/ build to fail in systems
such as Alpine Linus, that uses the Musl libc, so we need an alternative
way of having __WORDSIZE available, use the one used by
tools/include/linux/bitops.h, that builds in all the systems I have
build containers for.

These differences will be resolved at some point, so keep the warning in
check-headers.sh as a reminder.
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: John Garry <john.garry@huawei.com>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Kim Phillips <kim.phillips@amd.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: bpf@vger.kernel.org
Cc: kp singh <kpsingh@chromium.org>
Cc: netdev@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200515221732.44078-5-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>