* remove BindgenAttrs from other backend::ast structs
This is primarily a tool for use with the macro crate. Most of
these attributes were ignored in the actual codegen, but a few
were still being used. This is confusing when trying to add
other sources for codegen (such as webidl and typescript).
* move parsing logic to macro crate
This makes the backend crate solely concerned with having an ast
for which we can generate code.
* No need for version deps in dev-deps
These are all internal so we can drop the version
* Remove wasm-bindgen-cli's parity-wasm dep
No longer needed
* Tweak file hierarchy in webidl tests
Use Cargo's conventions to avoid the need to define `[[test]]` sections
* Remove unused imports
This is still a work in progress. Parse WebIDL source text and convert it into
wasm-bindgen AST, so that we can automatically emit bindings for the types and
functions described in the WebIDL.
