perf tools: Work around strict aliasing related warnings

Older versions of GCC are rather stupid about strict aliasing:

  util/trace-event-parse.c: In function 'parse_cmdlines':
  util/trace-event-parse.c:93: warning: dereferencing type-punned pointer will break strict-aliasing rules
  util/trace-event-parse.c: In function 'parse_proc_kallsyms':
  util/trace-event-parse.c:155: warning: dereferencing type-punned pointer will break strict-aliasing rules
  util/trace-event-parse.c:157: warning: dereferencing type-punned pointer will break strict-aliasing rules
  util/trace-event-parse.c:158: warning: dereferencing type-punned pointer will break strict-aliasing rules
  util/trace-event-parse.c: In function 'parse_ftrace_printk':
  util/trace-event-parse.c:294: warning: dereferencing type-punned pointer will break strict-aliasing rules
  util/trace-event-parse.c:295: warning: dereferencing type-punned pointer will break strict-aliasing rules
  make: *** [util/trace-event-parse.o] Error 1

Make it clear to GCC that we intend with those pointers, by passing
them through via an explicit (void *) cast.

We might want to add -fno-strict-aliasing as well, like the kernel
itself does.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>