JS codegen enhancements; still unusable

todo.txt

@@ -42,6 +42,10 @@ Bugs
 version 0.9.XX
 ==============
 
+- JS gen:
+  - document it
+  - test & fix bugs
+
 - document nimdoc properly finally
 - implement a warning message for shadowed 'result' variable
 - implement the high level optimizer
@@ -51,7 +55,6 @@ version 0.9.XX
 - implicit ref/ptr->var conversion; the compiler may store an object
   implicitly on the heap for write barrier efficiency; better: 
   proc specialization in the code gen
-- 'of' operator for JS backend
 - tlastmod returns wrong results on BSD (Linux, MacOS X: works)
 - nested tuple unpacking; tuple unpacking in non-var-context
 - 'nimrod def': does not always work?