perf scripting python: Expose symbol offset and source information

This change adds the symbol offset to the data exported for each
call-chain entry. This can not be calculated from the script and
only the ip value, and no related mmap information.

In addition, also export the source file and line information, if
available, to avoid an external lookup if this information is needed.

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/164554263724.752731.14651017093796049736.stgit@wsfd-netdev64.ntdv.lab.eng.bos.redhat.com


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