Removed Haiku64Image, it's not used any more.
Introduce vnode op supports_operation(), fix devfs_io()

devfs_io() can't fall back to calling vfs_synchronous_io(), if the
device driver doesn't support handling requests asynchronously. The
presence of the io() hook leads the VFS (do_iterative_fd_io()) to
believe that asynchronous handling is supported and set a
finished-callback on the request which calls the io() hook to start the
next chunk. Thus, instead of iterating through the request in a loop
the iteration happens recursively. For sufficiently fragmented requests
the stack may overflow (ticket #9900).

* Introduce a new vnode operation supports_operation(). It can be called
  by the VFS to determine whether a present hook is actually currently
  supported for a given vnode.
* devfs: implement the new hook and remove the fallback handling in
  devfs_io().
* vfs_request_io.cpp: use the new hook to determine whether the io()
  hook is really supported.