Use FIXME instead of TODO

Author: Zoxc

src/test/compile-fail/generator/borrowing.rs

@@ -23,7 +23,7 @@ fn main() {
     let _b = {
         let a = 3;
         || {
-            let _: () = gen arg; // TODO: shouldn't be needed for inference
+            let _: () = gen arg; // FIXME: shouldn't be needed for inference
             yield &a
             //~^ ERROR: `a` does not live long enough
         }

src/test/run-pass/generator/drop-env.rs

@@ -59,7 +59,7 @@ fn t2() {
 fn t3() {
     let b = B;
     let foo = || {
-        let _: () = gen arg; // TODO: this line should not be necessary
+        let _: () = gen arg; // FIXME: this line should not be necessary
         yield;
         drop(b);
     };