perf tools: Add missing headers, mostly stdlib.h

Part of the erosion of util/util.h, that will lose its include stdlib.h,
we need to add it to places where it is needed but was getting it
indirectly.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-1imnqezw99ahc07fjeb51qby@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>