libperf: Move to tools/lib/perf

Move libperf from its current location under tools/perf to a separate
directory under tools/lib/.

Also change various paths (mainly includes) to reflect the libperf move
to a separate directory and add a new directory under MANIFEST.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191206210612.8676-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/perf/Makefile

@@ -60,7 +60,7 @@ else
 endif
 
 INCLUDES = \
--I$(srctree)/tools/perf/lib/include \
+-I$(srctree)/tools/lib/perf/include \
 -I$(srctree)/tools/lib/ \
 -I$(srctree)/tools/include \
 -I$(srctree)/tools/arch/$(SRCARCH)/include/ \