perf symbols: Support for Openembedded/Yocto -dbg packages

perf symbols: Support for Openembedded/Yocto -dbg packages

On OpenEmbedded the symbol files are located under a .debug folder on
the same folder as the binary file.

This patch adds support for such files.

Without this patch on perf top you can see:

no symbols found in /usr/lib/gstreamer-1.0/libtheoraenc.so.1.1.2, maybe
install a debug package?

84.56%  libtheoraenc.so.1.1.2       [.] 0x000000000000b346

With this patch symbols are shown:

19.06%  libtheoraenc.so.1.1.2       [.] oc_int_frag_satd_thresh_mmxext
9.76%   libtheoraenc.so.1.1.2       [.] oc_analyze_mb_mode_luma
5.58%   libtheoraenc.so.1.1.2       [.] oc_qii_state_advance
4.84%   libtheoraenc.so.1.1.2       [.] oc_enc_tokenize_ac
...

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Waiman Long <Waiman.Long@hp.com>
Link: http://lkml.kernel.org/r/1379512574-25912-1-git-send-email-ricardo.ribalda@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>