Rather than representing a use as a pointer to an HValue and then searching
for the specific (ambiguous) operand, we now represent a use as a pair of an
HValue and the input operand index.  Additionally, use a linked list instead
of a growable array list since we never use random access.

This allows us to remove a bunch of similarly named and subtly different
functions from the HValue API.  The cost in extra zone allocation per use is
partially offset by reusing use list nodes when replacing a use of one value
with another.

R=danno@chromium.org,fschneider@chromium.org

Review URL: http://codereview.chromium.org/6881044

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@7674 ce2b1a6d-e550-0410-aec6-3dcde31c8c00