Add libpolicy stub-implementation to Android.mk

libpolicy is installed directly as "policy" in Chrome OS, so this patch
moves the chromeos/policy directory one level up to match what users will
see in installed Chrome OS include dir. A new libchromeos-policy shared
library is included in the Android.mk.

BUG: 23555535
TEST=emerge-link libchromeos; `mm` in aosp.

Change-Id: I0d62a1651632242a08309ca2c00056837a5280a6
17 files changed