Make moves explicit in doc examples

Had to remove the buffalo example. It was awkward to update for
explicit moves.

src/test/run-pass/issue-3668.rs

@@ -0,0 +1,13 @@
+struct P { child: Option<@mut P> }
+trait PTrait {
+   fn getChildOption() -> Option<@P>;
+}
+
+impl P: PTrait {
+   fn getChildOption() -> Option<@P> {
+       const childVal: @P = self.child.get();
+       fail;
+   }
+}
+
+fn main() {}

src/test/run-pass/issue-3688-2.rs

@@ -0,0 +1,5 @@
+   fn f(x:int) {
+       const child: int = x + 1;
+   }
+
+fn main() {}