Unignore a few tests

Also, remove one that has an exact duplicate.

Author: Jakub Wieczorek

src/test/compile-fail/non-constant-expr-for-fixed-len-vec.rs

@@ -8,10 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// ignore-test
-//
-// Ignored because of an ICE at the moment.
-
 // Check that non-constant exprs do fail as count in fixed length vec type
 
 fn main() {

src/test/run-pass/dead-code-one-arm-if.rs

@@ -10,8 +10,6 @@
 
 #![allow(unreachable_code)]
 
-// ignore-test #12920
-
 fn dont_call_me() { fail!(); println!("{}", 1); }
 
 pub fn main() { }

src/test/run-pass/parse-fail.rs

@@ -8,28 +8,26 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// ignore-test
 // Testing that supertrait methods can be called on subtrait object types
-// It's not clear yet that we want this
 
 trait Foo {
-    fn f() -> int;
+    fn f(&self) -> int;
 }
 
 trait Bar : Foo {
-    fn g() -> int;
+    fn g(&self) -> int;
 }
 
 struct A {
     x: int
 }
 
 impl Foo for A {
-    fn f() -> int { 10 }
+    fn f(&self) -> int { 10 }
 }
 
 impl Bar for A {
-    fn g() -> int { 20 }
+    fn g(&self) -> int { 20 }
 }
 
 pub fn main() {