Bug 1073842 - Finish renaming ObjectImpl to NativeObject, sr=luke.

--HG--
rename : js/src/vm/ObjectImpl-inl.h => js/src/vm/NativeObject-inl.h
rename : js/src/vm/ObjectImpl.cpp => js/src/vm/NativeObject.cpp
rename : js/src/vm/ObjectImpl.h => js/src/vm/NativeObject.h