max heap size on 64 bit from ca. 300Mbytes to ca. 200Mbytes
on Ulan's splay variant.  On 32 bit not much change.
Review URL: http://codereview.chromium.org/8494012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9906 ce2b1a6d-e550-0410-aec6-3dcde31c8c00