Add tests for blocks that must not have results

src/test/compile-fail/block-must-not-have-result-do.rs

@@ -0,0 +1,7 @@
+// error-pattern:this block must not have a result
+
+fn main() {
+    do {
+        true
+    } while true;
+}

src/test/compile-fail/block-must-not-have-result-for.rs

@@ -0,0 +1,7 @@
+// error-pattern:this block must not have a result
+
+fn main() {
+    for i in [0] {
+        true
+    }
+}

src/test/compile-fail/block-must-not-have-result-res.rs

@@ -0,0 +1,8 @@
+// error-pattern:this block must not have a result
+
+resource r(i: int) {
+    true
+}
+
+fn main() {
+}

src/test/compile-fail/block-must-not-have-result-while.rs

@@ -0,0 +1,7 @@
+// error-pattern:this block must not have a result
+
+fn main() {
+    while true {
+        true
+    }
+}