Merged r19693, r19694 into 3.23 branch.

Fix HConstants with Smi-ranged HeapNumber values

Fix for failing asserts in HBoundsCheck code generation on x64: use proper cmp operation width instead of asserting that Integer32 values should be zero extended. Similar to chromium:345820.

BUG=349878,349465
LOG=N
R=machenbach@chromium.org

Review URL: https://codereview.chromium.org/198503004

git-svn-id: https://v8.googlecode.com/svn/branches/3.23@19982 ce2b1a6d-e550-0410-aec6-3dcde31c8c00