Reviewed by John.

    Reviewed by John.

	<rdar://problem/4086819> Avoid using protect count hash table so much for 5.6% JS iBench speedup

	- Avoid using protected values hash for the two most common cases
	- Bump up ListImp high water mark, new testing shows 508 ListImps are
	created during JS iBench.

	Net result is a 5.6% speedup on JavaScript iBench

        * kjs/collector.cpp:
        (KJS::Collector::collect): mark protected lists as appropriate.
        * kjs/context.h:
        * kjs/list.cpp:
        (KJS::ListImp::markValues): Moved implementation from List::markValues
        (KJS::List::markProtectedLists): Implemented - scan pool and overflow
	list.
        (KJS::allocateListImp): link lists outside the pool into a separate
	doubly linked list to be able to mark protected lists
        (KJS::deallocateListImp): do the corresponding delinking
        (KJS::List::derefValues): do nothing in conservative GC mode
        (KJS::List::refValues): do nothing in conservative GC mode
        (KJS::List::markValues): call ListImp version
        (KJS::List::append):
        * kjs/list.h:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@9003 268f45cc-cd09-0410-ab3c-d52691b4dbfc