Move the option type to its own module

src/lib/util.rs

@@ -1,21 +1,3 @@
-tag option[T] {
-    none;
-    some(T);
-}
-
-type operator[T, U] = fn(&T) -> U;
-
-fn option_map[T, U](&operator[T, U] f, &option[T] opt) -> option[U] {
-    alt (opt) {
-        case (some[T](?x)) {
-            ret some[U](f(x));
-        }
-        case (none[T]) {
-            ret none[U];
-        }
-    }
-}
-
 fn id[T](&T x) -> T {
     ret x;
 }