perf tools: Add call-graph option support into .perfconfig

Adding call-graph option support into .perfconfig file, so it's now
possible use call-graph option like:

  [top]
        call-graph = fp

  [record]
        call-graph = dwarf,8192

Above options ONLY setup the unwind method. To enable perf record/top to
actually use it the command line option -g/-G must be specified.

The --call-graph option overloads .perfconfig setup.

Assuming above configuration:

  $ perf record -g ls
  - enables dwarf unwind with user stack size dump 8192 bytes

  $ perf top -G
  - enables frame pointer unwind

  $ perf record --call-graph=fp ls
  - enables frame pointer unwind

  $ perf top --call-graph=dwarf,4096 ls
  - enables dwarf unwind with user stack size dump 4096 bytes

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1391427883-13443-2-git-send-email-jolsa@redhat.com


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