Bug 743436 - remove XPCJSRuntime::mJSCycleCollectionContext and related code. r=peterv

The patch removes no longer used XPCJSRuntime::mJSCycleCollectionContext,
nsXPConnect::mCycleCollectionContext and related code to create/destroy
contexts. As that made nsCycleCollectionJSRuntime::FinishTraverse() empty
in all cases I removed that method as well.
Bug 846955 - Codegen Argument definitions using .define() in ClassDestructor::define. r=bz