libcore: Remove mutable fields from os and ptr

src/libcore/os.rs

@@ -352,7 +352,10 @@ pub fn fsync_fd(fd: c_int, _l: io::fsync::Level) -> c_int {
     }
 }
 
-pub struct Pipe { in: c_int, out: c_int }
+pub struct Pipe {
+    in: c_int,
+    out: c_int
+}
 
 #[cfg(unix)]
 pub fn pipe() -> Pipe {

src/libcore/ptr.rs

@@ -336,7 +336,10 @@ pub mod ptr_tests {
     #[test]
     fn test() {
         unsafe {
-            struct Pair {mut fst: int, mut snd: int};
+            struct Pair {
+                fst: int,
+                snd: int
+            };
             let mut p = Pair {fst: 10, snd: 20};
             let pptr: *mut Pair = &mut p;
             let iptr: *mut int = cast::transmute(pptr);