efl_io_model: next try to fix this race condition

efl_io_model: next try to fix this race condition

what is happening is that a file gets announced through eio_model
listing code, at this point of time, the monitor does not yet know about
the file. If the file now gets deleted between the annoncing and the
learning of the file from the monitor, then the file got an ADD event,
but no DEL event. Which is a bug.

With this commit there is a new API which asks the monitor if the file
already has the knowledge about the files existance, or not. A few
monitors like win32 inotify or cocoa do not have context about the file
directly, if the OS is now having the same bug, then we are again in
trouble, however, we canot do anything about that. In the case of kevent
or poll, this asks the context of the monitor if the file is already
there.

Reviewed-by: Cedric BAIL <cedric.bail@free.fr>
Differential Revision: https://phab.enlightenment.org/D10006