Merged r19591, r19599 into 3.23 branch.

HAllocate should never generate allocation code if the requested size does not fit into page. Regression test included.

Fix representation generalization for doubles.

BUG=347543
LOG=N
R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/180703004

git-svn-id: https://v8.googlecode.com/svn/branches/3.23@19630 ce2b1a6d-e550-0410-aec6-3dcde31c8c00