Introduce internal Log class that handles writing log messages, enable logging to...

Introduce internal Log class that handles writing log messages, enable logging to memory buffer.

This will enable reading profiler log in Chrome. The current implementation of memory buffer is trivial (fixed size buffer, no memory recycling) but enough to start end-to-end DevTools Profiler implementation. Later it will be enhanced.

Review URL: http://codereview.chromium.org/108011

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1870 ce2b1a6d-e550-0410-aec6-3dcde31c8c00