LibJS: Integrate labels into the Interpreter

The interpreter now considers a statement or block's label when
considering whether or not to break. All statements can be labelled.

Libraries/LibJS/Tests/labels.js

@@ -1,12 +1,42 @@
 load("test-common.js");
 
 try {
-    test:
-    {
+    test: {
         let o = 1;
         assert(o === 1);
+        break test;
+        assertNotReached();
     }
 
+    outer: {
+        {
+            break outer;
+        }
+        assertNotReached();
+    }
+
+    let counter = 0;
+    outer:
+    for (a of [1, 2, 3]) {
+        for (b of [4, 5, 6]) {
+            if (a === 2 && b === 5)
+                break outer;
+            counter++;
+        }
+    }
+    assert(counter === 4);
+
+    let counter = 0;
+    outer:
+    for (a of [1, 2, 3]) {
+        for (b of [4, 5, 6]) {
+            if (b === 6)
+                continue outer;
+            counter++;
+        }
+    }
+    assert(counter === 6);
+
     console.log("PASS");
 } catch (e) {
     console.log("FAIL: " + e);