perf script perl/python: Fix libexec scripts path in Documentation

The libexec path is /libexec/perf-core/scripts/*/Perf-Trace-Util.

Signed-off-by: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/1345391182-71825-1-git-send-email-dsahern@gmail.com


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