perf trace/scripting: Add Fedora libperl install note to doc

Fedora needs perl-ExtUtils-Embed for Perl scripting, which also
brings along libperl-devel; note this info for the convenience
of Fedora users.

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
Cc: anton@samba.org
Cc: hch@infradead.org
LKML-Reference: <1259565529-6407-5-git-send-email-tzanussi@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>