This sets the limit to 128M elements on all platforms. Before allocating a large array may
cause an OutOfMemory on x64 whereas it would not on ia32.

Also remove an unused constant from the FreeSpace class.

BUG=103103
Review URL: http://codereview.chromium.org/8637015

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10044 ce2b1a6d-e550-0410-aec6-3dcde31c8c00