Auto merge of #469 - fitzgen:enhanced-clang-ast-dumping, r=emilio
Auto merge of #469 - fitzgen:enhanced-clang-ast-dumping, r=emilio

Enhance Clang AST dumping

This commit extends our existing Clang AST dumping to include more information,
such as a cursor's canonical, referenced, and declarations cursors if they
exist. It prints out most of the information that libclang gives us directly,
but not the information that we attempt to (re)construct on top of the libclang
APIs.

r? @emilio or @Yamakaky

emilio/rust-bindgen,emilio/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,rust-lang/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen,emilio/rust-bindgen