Implement Element.className
implemented Node.normalize()
Update mozjs.
auto merge of #1921 : Ms2ger/servo/inhibit, r=jdm
auto merge of #1907 : brunoabinader/servo/element-classname, r=Ms2ger

Removes stub implementation from HTMLElement & implements logic in Element WebIDL.
auto merge of #1894 : khodzha/servo/node_normalize, r=Ms2ger

To resolve issue #1823 (without DOM Range updates)