Add METADATA / Licensing info am: 71df68510f am: 93412e4e7c am: c041837a6c

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/structopt-derive/+/1322914

Change-Id: I8e2224e2e4201f5cd0943e6c4de74bf1fe28f3d3