Clean up the top level directory a bit by moving all the helper libraries
to util/*.[ch].
Signed-off-by: Ingo Molnar <mingo@elte.hu>

First very raw version at having a central 'perf' command and
a list of subcommands:

  perf top
  perf stat
  perf record
  perf report
  ...

This is done by picking up Git's collection of utility functions,
and hacking them to build fine in this new environment.
Signed-off-by: Ingo Molnar <mingo@elte.hu>