Revert "staging, android: remove lowmemory killer from the tree"

This reverts commit 915e70f9.
Restore the kernel low memory killer as an alternative implementation
to the android userspace low memory killer.

Change-Id: I2b1e91a7bc4261cd1a8a23ae69b128d113069441
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>