CRAS: cras_shm module in libcras crate

cras_shm is a module for shared memory resources between cras_client and
cras_server, which are cras_server_state and cras_audio_shm_area.

BUG=chromium:907520
TEST=Run unit tests in modules by
     $ cargo test
TEST=Apply full patch set to test
     $ cras_tests /path/to/playback.raw

Change-Id: I927e5e2f24d794fc808396cc716d069bea3d0a4d
Reviewed-on: https://chromium-review.googlesource.com/1314276
Commit-Ready: Chih-Yang Hsia <paulhsia@chromium.org>
Tested-by: Chih-Yang Hsia <paulhsia@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
4 files changed