fix expected output of pretty/cast-lt and issue-4264 tests

Author: tinco

src/test/pretty/cast-lt.pp

@@ -3,7 +3,7 @@
 #[prelude_import]
 use std::prelude::v1::*;
 #[macro_use]
-extern crate std as std;
+extern crate std;
 // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
@@ -21,4 +21,3 @@
 macro_rules! negative(( $ e : expr ) => { $ e < 0 });
 
 fn main() { (1 as i32) < 0; }
-

src/test/pretty/cast-lt.rs

@@ -19,4 +19,3 @@ macro_rules! negative {
 fn main() {
       negative!(1 as i32);
 }
-

src/test/pretty/issue-4264.pp

@@ -1,7 +1,7 @@
 #[prelude_import]
 use std::prelude::v1::*;
 #[macro_use]
-extern crate std as std;
+extern crate std;
 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.