perf tools: Integrating the CoreSight decoding library

The Open CoreSight Decoding Library (openCSD) is a free and open library
to decode traces collected by the CoreSight hardware infrastructure.

This patch adds the required mechanic to recognise the presence of the
openCSD library on a system and set up miscellaneous flags to be used in
the compilation of the trace decoding feature.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kim Phillips <kim.phillips@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Mike Leach <mike.leach@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Link: http://lkml.kernel.org/r/1516211539-5166-2-git-send-email-mathieu.poirier@linaro.org
Link: http://lkml.kernel.org/r/1516635644-24819-1-git-send-email-mathieu.poirier@linaro.org
[ Merged missing test-libopencsd.c file, provided later by Mathieu ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>