Limit the number of transitions allowed per hidden class.

Each time a transition is added to a hidden class, the whole
transitions array must be copied, which causes poor performance
in some circumstances.  This change limits the maximum size of
the transition array, avoiding this behavior in the pathological
case.  For example, this improves the performance of the EtchMark
benchmark by nearly 60%.

BUG=v8:3616
LOG=
R=verwaest@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/635883003

Patch from Kevin M. McCormick <mckev@amazon.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24857 ce2b1a6d-e550-0410-aec6-3dcde31c8c00