Perf build fails with the new rbtree implementation:

  ../../lib/rbtree.c:24:36: fatal error: linux/rbtree_augmented.h: No such file or directory compilation terminated.

Fix by updating the Makefile and adding a btree_augmented.h
wrapper.
Reported-and-tested-by: NBorislav Petkov <borislav.petkov@amd.com>
Signed-off-by: NMarkus Trippelsdorf <markus@trippelsdorf.de>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Borislav Petkov <bp@amd64.org>
Link: http://lkml.kernel.org/r/20121009180156.GA245@x4Signed-off-by: NIngo Molnar <mingo@kernel.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>