perf tools: Fix segfault for symbol annotation on TUI

Currently the symbol structure is allocated with symbol_conf.priv_size
to carry sideband information like annotation, map browser on TUI and
sort-by-name tree node.  So retrieving these information from symbol
needs to care about the details of such placement.

However the annotation code just assumes that the symbol is placed after
the struct annotation.  But actually there's other info between them.
So accessing those struct will lead to an undefined behavior (usually a
crash) after they write their info to the same location.

To reproduce the problem, please follow the steps below:

  1. run perf report (TUI of course) with -v option
  2. open map browser (by pressing right arrow key for any entry)
  3. search any function (by pressing '/' key and input whatever..)
  4. return to the hist browser (by pressing 'q' or left arrow key)
  5. open annotation window for the same entry (by pressing 'a' key)

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1421234288-22758-1-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>