Bump protobuf for Bazel 0.21 (#1493)
Bump protobuf for Bazel 0.21 (#1493)

Protobuf 3.5 would require a Bazel flag
bazel build --incompatible_package_name_is_a_function=false
for Bazel 0.21 because its bazel syntax is old.
Rather than building with this flag, let's just update
the protobuf version.

Also, fix lint.
wohe/cartographer,googlecartographer/cartographer,googlecartographer/cartographer,cartographer-project/cartographer,wohe/cartographer,damonkohler/cartographer,cartographer-project/cartographer,larics/cartographer,larics/cartographer,googlecartographer/cartographer,googlecartographer/cartographer,larics/cartographer,wohe/cartographer,damonkohler/cartographer,damonkohler/cartographer,cartographer-project/cartographer,damonkohler/cartographer,cartographer-project/cartographer,wohe/cartographer,larics/cartographer