Testcase typo and other trivia fixes

ecmascript-testcases/test-dev-mandel3.js

@@ -127,7 +127,7 @@ for (i = 0; i - h; i += 1) {
             }
         }
 
-	res = res + ' ' + colors[k];
+        res = res + ' ' + colors[k];
     }
 
     print(res);

ecmascript-testcases/test-dev-sandbox-prototype-limitation.js

@@ -1,7 +1,7 @@
 /*
  *  There is currently (Duktape 1.0) no way to prevent user code from
  *  accessing built-in prototype objects through plain values.  For
- *  example, a plain string implicitly inherites from the original
+ *  example, a plain string implicitly inherits from the original
  *  String.prototype.
  */