perf c2c report: Allow to set cacheline sort fields

Allowing user to configure the way the single cacheline
data are sorted after being sorted by offset.

Adding 'c' option to specify sorting fields for single cacheline:

    -c, --coalesce <coalesce fields>
                          coalesce fields: pid,tid,iaddr,dso

It's allowed to use following combination of fields:
  pid   - process pid
  tid   - process tid
  iaddr - code address
  dso   - shared object

Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-aka8z31umxoq2gqr5mjd81zr@git.kernel.org


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