unxfail-test and try to test for similar conditions as before

fixes #2772

Author: nikomatsakis

src/test/compile-fail/liveness-closure-require-ret.rs

@@ -1,4 +1,2 @@
-// xfail-test After the closure syntax change this started failing with the wrong error message
-// error-pattern: not all control paths return
 fn force(f: fn() -> int) -> int { f() }
-fn main() { log(error, force(|| {})); }
+fn main() { log(debug, force(|| {})); } //~ ERROR mismatched types

src/test/compile-fail/liveness-issue-2163.rs

@@ -1,6 +1,5 @@
-// xfail-test After the closure syntax change this started failing with the wrong error message
-fn main(_s: ~[str]) {
+fn main() {
     let a: ~[int] = ~[];
-    do vec::each(a) |_x| { //~ ERROR not all control paths return a value
-    }
+    vec::each(a, fn@(_x: int) -> bool { //~ ERROR not all control paths return a value
+    });
 }