Merged r19535, r19549, r19586, r19584 into trunk branch.

Fix for a smi stores optimization on x64 with a regression test.

Fix for failing asserts in HBoundsCheck code generation on x64: index register should be zero extended.

Fix putting of prototype transitions. The length is also subject to GC, just like entry.

Handle arguments objects in frame when materializing arguments

BUG=345715,345820,347536,347262
LOG=N
R=danno@chromium.org

Review URL: https://codereview.chromium.org/183353002

git-svn-id: https://v8.googlecode.com/svn/trunk@19589 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/trunk' into trunk