Out of the code to write the cpu topology map in the perf.data file
header.

Now if one needs the CPU topology map for the running machine, one needs
to call perf_env__read_cpu_topology_map(perf_env) and the info will be
stored in perf_env.cpu.

For now we're using a global perf_env variable, that will have its
contents freed after we run a builtin.

v2: Check perf_env__read_cpu_topology_map() return in
    write_cpu_topology() (Kan Liang)

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1441828225-667-5-git-send-email-acme@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Move this from two globals to perf_env global, that eventually will
be just perf_header->env or something else, to ease the refactoring
series, leave it as a global and go on reading more of its fields,
not as part of the header writing process but as a perf_env init one
that will be used for perf.data-less situations.

Tested-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-2j78tdf8zn1ci0y6ji15bifj@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Since it can be used separately from 'perf_session' and 'perf_header',
move it to separate include file and object, next csets will try to move
a perf_env__init() routine.

Tested-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-ff2rw99tsn670y1b6gxbwdsi@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>