Allow google dialer code to be compiled against M and N SDKs

+ Class DirectorySdkCompat and PhoneAccountSdkCompat for N/pre-N version
  pre-N is implemented with stubs

Bug:26330692
Change-Id: I53374f68ff3756ba0a502c15d07aa18a2d763e83
3 files changed
tree: f3178f6469e117d27c6d31dc8186de4e9da99b47
  1. src/
  2. TestCommon/
  3. tests/