tools/perf: Support sorting by in_tx or abort branch flags

Extend the perf branch sorting code to support sorting by in_tx
or abort_tx qualifiers. Also print out those qualifiers.

This also fixes up some of the existing sort key documentation.

We do not support no_tx here, because it's simply not showing
the in_tx flag.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1379688044-14173-4-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>