Fix trivial error when building with clang.

$ ninja -C out/Debug
...

../../src/d8.cc:171:11: error: unused variable 'MB'
[-Werror,-Wunused-const-variable]
const int MB = 1024 * 1024;
          ^
          1 error generated.

R=titzer@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/105833008

Patch from Thiago Farina <tfarina@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18276 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Avoid FP exceptions when doing integer division.

BUG=v8:3039
R=titzer@chromium.org

Review URL: https://codereview.chromium.org/104003004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18277 ce2b1a6d-e550-0410-aec6-3dcde31c8c00