std: Add cell to the std crate and make it build

Author: brson

src/libstd/cell.rs

@@ -18,18 +18,18 @@ fn empty_cell<T>() -> Cell<T> {
 impl<T> Cell<T> {
     /// Yields the value, failing if the cell is empty.
     fn take() -> T {
-        let value = none;
+        let mut value = none;
         value <-> self.value;
         if value.is_none() {
-            fail "attempt to take an empty cell";
+            fail ~"attempt to take an empty cell";
         }
         return option::unwrap(value);
     }
 
     /// Returns the value, failing if the cell is full.
     fn put_back(+value: T) {
         if self.value.is_none() {
-            fail "attempt to put a value back into a full cell";
+            fail ~"attempt to put a value back into a full cell";
         }
         self.value = some(move value);
     }
@@ -39,4 +39,3 @@ impl<T> Cell<T> {
         self.value.is_none()
     }
 }
-

src/libstd/std.rc

@@ -26,6 +26,7 @@ export ebml, dbg, getopts, json, rand, sha1, term, time, prettyprint;
 export test, tempfile, serialization;
 export cmp;
 export base64;
+export cell;
 
 // General io and system-services modules
 
@@ -45,6 +46,7 @@ mod uv_global_loop;
 
 mod c_vec;
 mod timer;
+mod cell;
 
 // Concurrency