Magic fix for Math.sin/cos.

It turns out that Sunspider 1.0's 3d-morph verifies that the floating
point error must start with 6.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/61593008

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17725 ce2b1a6d-e550-0410-aec6-3dcde31c8c00