pref_counter: tools: report: Add header printout & prettify

pref_counter: tools: report: Add header printout & prettify

Old default output:

 3.12%    perf-report [.] ./perf-report:       dsos__find
 2.44%    perf-report [k] kernel:              kallsyms_expand_symbol
 2.28%          :4483 [.] <unknown>:           <unknown>
 2.05%          :4174 [k] kernel:              _spin_lock_irqsave
 2.01%    perf-report [k] kernel:              vsnprintf
 1.92%    perf-report [k] kernel:              format_decode
 1.92%          :4438 [k] kernel:              _spin_lock

New default output:

 #
 # Overhead          Command       File: Symbol
 # ........          .......       ............
 #
      6.54%             perf  [k]  kernel: kallsyms_expand_symbol
      6.26%             perf  [.]  /home/mingo/tip/Documentation/perf_counter/perf: dso__insert_symbol
      4.76%             perf  [.]  /home/mingo/tip/Documentation/perf_counter/perf: hex2long
      4.55%             perf  [k]  kernel: number
      4.48%             perf  [k]  kernel: format_decode
      4.09%             perf  [k]  kernel: vsnprintf

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20090527182101.229504802@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>