PDL: Remove unnecessary `extern crate`

//! PDL parser and linter.

extern crate codespan_reporting;

extern crate pest;

#[macro_use]

extern crate pest_derive;

extern crate serde;

extern crate serde_json;

extern crate structopt;

use codespan_reporting::term;

use codespan_reporting::term::termcolor;

use codespan_reporting::term::{self, termcolor};

use structopt::StructOpt;

mod ast;

// TODO: use #[grammar = "pdl.pest"]

// currently not possible because CARGO_MANIFEST_DIR is not set

// in soong environment.

#[derive(Parser)]

#[derive(pest_derive::Parser)]

#[grammar_inline = r#"

WHITESPACE = _{ " " | "\n" }

COMMENT = { block_comment | line_comment }