Rewrite SamplingCircularQueue

The new implementation:
* uses MemoryBarriers to make sure up-to-date data is accessed on both producer and consumer threads
* will not allow to overwrite records
* doesn't have notion of chunks, instead each entry is aligned on the cache line boundaries

BUG=v8:2814
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/22849002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@16284 ce2b1a6d-e550-0410-aec6-3dcde31c8c00