perf inject: Work with files

Before this patch "perf inject" can only handle data from pipe.

I want to use "perf inject" for reworking events. Look at my following patch.

v2: add information about new options in tools/perf/Documentation/

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344344165-369636-2-git-send-email-avagin@openvz.org
[ committer note: fixed it up to cope with 5852a445, 5ded57ac, 002439e8 & f62d3f0f

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