rustRegistry: 2016-09-29 -> 2016-10-29

Update the `rustRegistry` package from version 2016-09-29, revision
rust-lang/crates.io-index@12dc47026cadf5aa2823c9d0fdd055b9f2c0f52c, to
version 2016-10-29, revision
rust-lang/crates.io-index@623cc0d9328bfb949b54209443f2b4f06c41961e.

I have tested this patch per nixpkgs manual section 11.1 ("Making
patches").