Basic implementation of liveedit feature

test/mjsunit/debug-script.js

Index: test/mjsunit/debug-script.js
diff --git a/test/mjsunit/debug-script.js b/test/mjsunit/debug-script.js
index effa145dee34eec3e563a60a2a0137a1d1002cfc..402f90cf830c0c5e67f156b6f6b766635f5b8b19 100644
--- a/test/mjsunit/debug-script.js
+++ b/test/mjsunit/debug-script.js
@@ -52,7 +52,7 @@ for (i = 0; i < scripts.length; i++) {
 }
 
 // This has to be updated if the number of native scripts change.
-assertEquals(12, named_native_count);
+assertEquals(13, named_native_count);
 // If no snapshot is used, only the 'gc' extension is loaded.
 // If snapshot is used, all extensions are cached in the snapshot.
 assertTrue(extension_count == 1 || extension_count == 5);