perf tools: Fix srcline sort key behavior

perf tools: Fix srcline sort key behavior

Currently the srcline sort key compares ip rather than srcline info.  I
guess this was due to a performance reason to run external addr2line
utility.  Now we have implemented the functionality inside, use the
srcline info when comparing hist entries.

Also constantly print "??:0" string for unknown srcline rather than
printing ip.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Reviewed-by: Jiri Olsa <jolsa@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1378876173-13363-10-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>