Create StreamSocket for IO hooking implementation

Create StreamSocket for IO hooking implementation

Fixes the SSL SendQ bug
Removes duplicate code between User and BufferedSocket
Simplify SSL module API
Simplify EventHandler API (Readable/Writeable moved to SE)
Add hook for culled objects to invoke callbacks prior to destructor
 Replace SocketCull with GlobalCull now that sockets can close themselves
Shorten common case of user read/parse/write path:
 User::Write is now zero-copy up to syscall/SSL invocation
 User::Read has only two copy/scan passes from read() to ProcessCommand

git-svn-id: http://svn.inspircd.org/repository/trunk/inspircd@11752 e03df62e-2008-0410-955e-edbf42e46eb7