Releasing the former Stadia file transfer tools

The tools allow efficient and fast synchronization of large directory
trees from a Windows workstation to a Linux target machine.

cdc_rsync* support efficient copy of files by using content-defined
chunking (CDC) to identify chunks within files that can be reused.

asset_stream_manager + cdc_fuse_fs support efficient streaming of a
local directory to a remote virtual file system based on FUSE. It also
employs CDC to identify and reuse unchanged data chunks.

.gitmodules

@@ -0,0 +1,12 @@
+[submodule "third_party/absl"]
+	path = third_party/absl
+	url = https://github.com/abseil/abseil-cpp.git
+[submodule "third_party/protobuf"]
+	path = third_party/protobuf
+	url = https://github.com/google/protobuf.git
+[submodule "third_party/googletest"]
+	path = third_party/googletest
+	url = https://github.com/google/googletest.git
+[submodule "third_party/grpc"]
+	path = third_party/grpc
+	url = https://github.com/grpc/grpc.git