perf trace beauty: Export the pid beautifier for use in more places

Now that the beautifiers are being split into multiple source and object
files, we will need more of them exported, do it for the 'pid' one, will
be used to augment the return of some syscalls that may return a 'pid',
such as fcntl(fd, F_GETOWN).

Will also be used for fcntl(fd, F_SETOWN, pid).

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.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-7gr5nt9p5skp4i1w0ja1w272@git.kernel.org


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