perf sched: Use perf_tool as ancestor

So that we can remove all the globals.

Before:

   text	   data	    bss	    dec	    hex	filename
1586833	 110368	1438600	3135801	 2fd939	/tmp/oldperf

After:

   text	   data	    bss	    dec	    hex	filename
1629329	  93568	 848328	2571225	 273bd9	/root/bin/perf

Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-oph40vikij0crjz4eyapneov@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>