Changed all log messages to be handled through the LogMessageBuilder instead of through fprintf directly to the log file.

Added a flag for the runtime %Log call and fixed its arguments checking. Use of %Log is only for debugging.
Review URL: http://codereview.chromium.org/21406

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1290 ce2b1a6d-e550-0410-aec6-3dcde31c8c00