Merge #1743

1743: Support `#[macro_use]` on `extern crate` r=matklad a=uHOOCCOOHu

Unfortunately, #1688 is still an issue. My guess is wrong :(

Co-authored-by: uHOOCCOOHu <hooccooh1896@gmail.com>

crates/ra_syntax/src/ast/generated.rs

@@ -934,6 +934,7 @@ impl AstNode for ExternCrateItem {
         &self.syntax
     }
 }
+impl ast::AttrsOwner for ExternCrateItem {}
 impl ExternCrateItem {
     pub fn name_ref(&self) -> Option<NameRef> {
         AstChildren::new(&self.syntax).next()