Un-xfail some tests that work

Author: catamorphism

src/test/compile-fail/forgot-ret.rs

@@ -1,5 +1,4 @@
 // -*- rust -*-
-// xfail-stage0
 // error-pattern: not all control paths return
 
 fn god_exists(int a) -> bool {

src/test/compile-fail/pattern-tyvar.rs

@@ -1,6 +1,3 @@
-// xfail-stage0
-// xfail-stage1
-// xfail-stage2
 // -*- rust -*-
 use std;
 import std::option;

src/test/compile-fail/slot-as-pred.rs

@@ -1,9 +1,6 @@
-// xfail-stage0
-// xfail-stage1
-// xfail-stage2
 // -*- rust -*-
-
-// error-pattern: mismatched types
+// xfail-stage0
+// error-pattern: unresolved name: lt
 
 fn f(int a, int b) : lt(a,b) {
 }