perf beauty: Switch from GPL v2.0 to LGPL v2.1

The intention is to have this as a library, since it is not perf
specific at all.

I did the switch for the files where I'm the only contributor, with the
exception of a few lines changed by Jiri Olsa.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-a04q6chdyjknm1hr305ulx8h@git.kernel.org


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