Revert "Load/Store cannot handle double representation."

This reverts r17135 -- test crashes on x64.

TBR=bmeurer@chromium.org
BUG=

Review URL: https://codereview.chromium.org/26653004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17138 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
More precise type lub for numbers

R=jkummerow@chromium.org
BUG=v8:2910

Review URL: https://codereview.chromium.org/25722002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17139 ce2b1a6d-e550-0410-aec6-3dcde31c8c00