During bind and listen socket errors are now handled. If the listen socket is occoupied the agent will retry its bind operation until success or shutdown.

Added orderly shutdown of the debugger agent both with and without a client connected.
Review URL: http://codereview.chromium.org/50007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1552 ce2b1a6d-e550-0410-aec6-3dcde31c8c00