BUG=none
TEST=Added to test/mjsunit/math-floor-of-div.js, math-floor-of-div-nosudiv.js

Review URL: https://codereview.chromium.org/11316105
Patch from Martyn Capewell <m.m.capewell@googlemail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13257 ce2b1a6d-e550-0410-aec6-3dcde31c8c00