rustc-ap-serialize 504.0.0

Automatically published version of the package `serialize` in the rust-lang/rust repository from commit 9d5b6efdf62dbcd7bdf8e78a5f69c1b6678fd155 The publishing script for this crate lives at: https://github.com/alexcrichton/rustc-auto-publish

Support code for encoding and decoding types.