Fix rustc warning about unused Write trait.

cranelift/src/libcretonne/entities.rs

@@ -20,7 +20,7 @@
 //! format.
 
 use std::default::Default;
-use std::fmt::{self, Display, Formatter, Write};
+use std::fmt::{self, Display, Formatter};
 use std::u32;
 
 /// An opaque reference to an extended basic block in a function.

cranelift/src/libcretonne/types.rs

@@ -2,7 +2,7 @@
 //! Common types for the Cretonne code generator.
 
 use std::default::Default;
-use std::fmt::{self, Display, Formatter, Write};
+use std::fmt::{self, Display, Formatter};
 
 // ====--------------------------------------------------------------------------------------====//
 //

cranelift/src/libreader/parser.rs

@@ -7,7 +7,7 @@
 
 use std::collections::HashMap;
 use std::result;
-use std::fmt::{self, Display, Formatter, Write};
+use std::fmt::{self, Display, Formatter};
 use std::str::FromStr;
 use std::u32;
 use lexer::{self, Lexer, Token};