Spellchecking compiler comments

This PR cleans up the rest of the spelling mistakes in the compiler comments. This PR does not change any literal or code spelling issues.

compiler/rustc_ast/src/tokenstream.rs

@@ -295,7 +295,7 @@ impl AttrAnnotatedTokenStream {
 ///
 /// For example, `#[cfg(FALSE)] struct Foo {}` would
 /// have an `attrs` field containing the `#[cfg(FALSE)]` attr,
-/// and a `tokens` field storing the (unparesd) tokens `struct Foo {}`
+/// and a `tokens` field storing the (unparsed) tokens `struct Foo {}`
 #[derive(Clone, Debug, Encodable, Decodable)]
 pub struct AttributesData {
     /// Attributes, both outer and inner.