perf symbols: Implement poor man's ELF parser

Implement a minimal elf parser for getting build-id.  It assumes that
required elf.h header is provided by libc header on the system and the
parser only looks for PT_NOTE program header to check build-id.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
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/1344228082-15569-5-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>