Make sure that there is always room for RelocInfoWriter::kMaxSize
bytes in the buffer before writing to it. We only ensured space for 8
bytes, but relocation information can be up to 16 bytes in x64.

Review URL: http://codereview.chromium.org/2100010

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4683 ce2b1a6d-e550-0410-aec6-3dcde31c8c00