This sets the `catch` flag on the emitted AST when an operation/attribute has
the `[Throws]` extended attribute on it.
Additionally, constructors aren't annotated with `[Throws]` but can still throw
exceptions, so we must conservatively assume *every* constructor can throw an
error.
* webidl: Remove exact-output tests
These have not been as effective, nor as easy to write and maintain, as the
project()-based integration tests.
* tests: Move webidl tests into the webidl crate's test suite
* 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.
