NativeArray: Array.prototype.{indexOf, lastIndexOf} bug fixes
NativeArray: Array.prototype.{indexOf, lastIndexOf} bug fixes

- removed indexOfHelper method, indexOf and lastIndexOf now use seperate methods since the amount of shared lines was negliglible to justify the added non-uniformness compared to the other js_* methods
- 15.4.4.14  Array.prototype.indexOf uses [[Get]], therefore add search for prototype values in the dense-array case
- 15.4.4.15  Array.prototype.lastIndexOf uses [[Get]], therefore add search for prototype values in the dense-array case

AlexTrotsenko/rhino,ashwinrayaprolu1984/rhino,tuchida/rhino,sam/htmlunit-rhino-fork,Angelfirenze/rhino,Pilarbrist/rhino,AlexTrotsenko/rhino,Pilarbrist/rhino,sainaen/rhino,tejassaoji/RhinoCoarseTainting,Angelfirenze/rhino,tejassaoji/RhinoCoarseTainting,lv7777/egit_test,lv7777/egit_test,swannodette/rhino,sam/htmlunit-rhino-fork,Pilarbrist/rhino,sainaen/rhino,sam/htmlunit-rhino-fork,tejassaoji/RhinoCoarseTainting,Pilarbrist/rhino,sainaen/rhino,Pilarbrist/rhino,tejassaoji/RhinoCoarseTainting,tuchida/rhino,sainaen/rhino,swannodette/rhino,sainaen/rhino,tuchida/rhino,Angelfirenze/rhino,AlexTrotsenko/rhino,swannodette/rhino,sainaen/rhino,swannodette/rhino,tuchida/rhino,AlexTrotsenko/rhino,sam/htmlunit-rhino-fork,lv7777/egit_test,tejassaoji/RhinoCoarseTainting,lv7777/egit_test,ashwinrayaprolu1984/rhino,Angelfirenze/rhino,AlexTrotsenko/rhino,lv7777/egit_test,sam/htmlunit-rhino-fork,Angelfirenze/rhino,swannodette/rhino,tuchida/rhino,tejassaoji/RhinoCoarseTainting,ashwinrayaprolu1984/rhino,Angelfirenze/rhino,Pilarbrist/rhino,tuchida/rhino,sam/htmlunit-rhino-fork,sam/htmlunit-rhino-fork,sainaen/rhino,ashwinrayaprolu1984/rhino,AlexTrotsenko/rhino,swannodette/rhino,lv7777/egit_test,ashwinrayaprolu1984/rhino,Pilarbrist/rhino,tuchida/rhino,swannodette/rhino,Angelfirenze/rhino,lv7777/egit_test,ashwinrayaprolu1984/rhino,tejassaoji/RhinoCoarseTainting,AlexTrotsenko/rhino,ashwinrayaprolu1984/rhino