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