Reformat use declarations.

The previous commit updated `rustfmt.toml` appropriately. This commit is
the outcome of running `x fmt --all` with the new formatting options.

compiler/rustc_builtin_macros/src/lib.rs

@@ -21,11 +21,12 @@
 
 extern crate proc_macro;
 
-use crate::deriving::*;
 use rustc_expand::base::{MacroExpanderFn, ResolverExpand, SyntaxExtensionKind};
 use rustc_expand::proc_macro::BangProcMacro;
 use rustc_span::symbol::sym;
 
+use crate::deriving::*;
+
 mod alloc_error_handler;
 mod assert;
 mod cfg;