Fix test for warn_unused_result and move it to v8config.h.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/23546002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16347 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Skip failing test for NaCl.

The test was added in 16322 and fails on NaCl ever since.

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/23479003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16348 ce2b1a6d-e550-0410-aec6-3dcde31c8c00