--trace_hydrogen cleanup

--trace_hydrogen cleanup
    
* src/hydrogen.cc (HTracer::Trace): Remove from_bci and to_bci
  printouts (always -1), xhandlers and flags (always empty), and the bci
  column for instruction traces (always 0).
    
  Also remove <|@ ending, as all instruction traces fit on a line.  I
  googled and it seems the provenance of this goes back at least as far
  as hotspot!

BUG=
TEST=

[wingo, 2011-06-28 16:14:31]

I'm trying to understand some parts of Crankshaft, and I figure that if
I decide that something is crufty it's better to go ahead and push a fix
than make a note.  Please let me know if you would rather receive these
patches in some other manner, or not at all.

[Sven Panne, 2011-06-29 08:32:54]

The output of --trace-hydrogen is meant to be read and analyzed by the
C1visualizer tool (http://c1visualizer.java.net/), not by humans. With your
patch, C1visualizer becomes rather unhappy, so we cannot incorporate your
changes. Using the tool is much, much more convenient than reading hydrogen.cfg,
anyway... ;-)

[wingo, 2011-06-29 08:43:56]

> C1visualizer

Indeed, sorry for the noise; thanks anyway for the review!