LibJS: Add support for do..while statements

Author: https://github.com/awesomekling
Commit: f8393b80e3

Libraries/LibJS/Tests/do-while-basic.js

@@ -0,0 +1,17 @@
+function assert(x) { if (!x) throw 1; }
+
+try {
+    var number = 0;
+    do {
+        number++;
+    } while (number < 9);
+    assert(number === 9);
+
+    number = 0;
+    do number++; while(number < 3);
+    assert(number === 3);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}