Reviewed by Geoff Garen.

        On x86_64, make all JIT-code allocations from a new heap, managed
        by FixedVMPoolAllocator.  This class allocates a single large (2Gb)
        pool of virtual memory from which all further allocations take place.
        Since all JIT code is allocated from this pool, we can continue to
        safely assume (as is already asserted) that it will always be possible
        to link any JIT-code to JIT-code jumps and calls.

        * JavaScriptCore.xcodeproj/project.pbxproj:
            Add new file.
        * jit/ExecutableAllocatorFixedVMPool.cpp: Added.
        (JSC::FreeListEntry::FreeListEntry):
        (JSC::AVLTreeAbstractorForFreeList::get_less):
        (JSC::AVLTreeAbstractorForFreeList::set_less):
        (JSC::AVLTreeAbstractorForFreeList::get_greater):
        (JSC::AVLTreeAbstractorForFreeList::set_greater):
        (JSC::AVLTreeAbstractorForFreeList::get_balance_factor):
        (JSC::AVLTreeAbstractorForFreeList::set_balance_factor):
        (JSC::AVLTreeAbstractorForFreeList::null):
        (JSC::AVLTreeAbstractorForFreeList::compare_key_key):
        (JSC::AVLTreeAbstractorForFreeList::compare_key_node):
        (JSC::AVLTreeAbstractorForFreeList::compare_node_node):
        (JSC::sortFreeListEntriesByPointer):
        (JSC::sortCommonSizedAllocations):
        (JSC::FixedVMPoolAllocator::release):
        (JSC::FixedVMPoolAllocator::reuse):
        (JSC::FixedVMPoolAllocator::addToFreeList):
        (JSC::FixedVMPoolAllocator::coalesceFreeSpace):
        (JSC::FixedVMPoolAllocator::FixedVMPoolAllocator):
        (JSC::FixedVMPoolAllocator::alloc):
        (JSC::FixedVMPoolAllocator::free):
        (JSC::ExecutableAllocator::intializePageSize):
        (JSC::ExecutablePool::systemAlloc):
        (JSC::ExecutablePool::systemRelease):
            The new 2Gb heap class!
        * jit/ExecutableAllocatorPosix.cpp:
            Disable use of this implementation on x86_64.
        * wtf/AVLTree.h:
            Add missing variable initialization.
        (WTF::::remove):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@42638 268f45cc-cd09-0410-ab3c-d52691b4dbfc