from Value, and eliminate ReferenceImp.

	18% speedup on cvs-js-performance test.

        * kjs/internal.cpp, kjs/internal.h: Remove ReferenceImp.
        * kjs/nodes.cpp:
        (Node::evaluateReference): Use Reference::makeValueReference(),
	not ConstReference.
        * kjs/reference.cpp:
        (Reference::Reference): New implementation, handles both regular
	and value references.
        (Reference::makeValueReference): Incorporate functionality of ConstReference
	into this class.
        (Reference::getBase): New implementation (incorporates error vase
	for value references).
	(Reference::getPropertyName): New implementation (incorporates error case
	for value references).
        (Reference::putValue): New implementation (incorporates error case
	for value references).
        (Reference::deleteValue): New implementation (incorporates error case
	for value references).
        (Reference::getValue): New implementation (incorporates special case
	for value references).
        (Reference::isMutable): New implementation.
	* kjs/reference.h: New implementation that merges ReferenceImp
	into the stack object.
        * kjs/value.h, kjs/value.cpp: Removed all reference-related method.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@1850 268f45cc-cd09-0410-ab3c-d52691b4dbfc