Drop redundant GetRandomMmapAddr() in platform-openbsd.cc.

TBR=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/20284002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15874 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Move representation into HObjectAccess and remove from HLoadNamedField and HStoreNamedField.

BUG=
R=danno@chromium.org

Review URL: https://codereview.chromium.org/18503006

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15875 ce2b1a6d-e550-0410-aec6-3dcde31c8c00