Improve our simple elimination of hole checks.

Improve our simple elimination of hole checks.

Currently we avoid checking for the hole value after array loads, if the
result is only used by instructions that definitely deoptimize in case
of the hole value (HChange instructions).

This change performs the same procedure for loading from deleteable/read-only
global variable where we can also avoid the check in the same cases.
Review URL: http://codereview.chromium.org/8054008

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9453 ce2b1a6d-e550-0410-aec6-3dcde31c8c00