stdlib: Add Result and Option types

Since the type checker sucks less now, we can think about maybe
adding some features to the language.

...At some point I'd like to have the type checker clean up
the index map.

stdlib/std/option.cl

@@ -0,0 +1,21 @@
+//! The optional type, representing the presence or absence of a thing.
+
+pub enum Option<T> {
+    Some(T),
+    None,
+}
+
+impl Option {
+    pub fn is_some(self: &Self) -> bool {
+        match self {
+            Some(_) => true,
+            None => false,
+        }
+    }
+    pub fn is_none(self: &Self) -> bool {
+        match self {
+            Some(_) => false,
+            None => true,
+        }
+    }
+}