Fix loop splitting bug in NS2Dart.
First cut of converting NS2Dart to the interceptors strategy for using built-in basic types. Splay is somewhat faster (unwrapped strings?). DeltaBlue, Richards and ClosureFibonacci are much slower and ParserCombinators is somewhat slower (less direct path for closure invocation? megamorphic getInterceptor?). Compilation time is slower (double parsing the runtime sources to determine the intercepted selectors).