Version 3.26.13 (based on bleeding_edge revision r20698)

Make maps in monomorphic IC stubs weak (issue 2073).

x64: Make sure that the upper half of a 64bit register contains 0 for int32 values (Chromium issue 360611).

Performance and stability improvements on all platforms.

git-svn-id: https://v8.googlecode.com/svn/trunk@20699 ce2b1a6d-e550-0410-aec6-3dcde31c8c00