Disable unit test because of NaCL breakage after r23617.

TBR=bmeurer@chromium.org
TEST=base-unittests/BitsDeathTest.RoundUpToPowerOfTwo32

Review URL: https://codereview.chromium.org/532713002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23621 ce2b1a6d-e550-0410-aec6-3dcde31c8c00