w3m-submit-form needs child-safety hook

[jidanni@xxxxxxxxxxx]

"C-c C-c runs the command w3m-submit-form"
which is too dangerous. Why? Because it is too easy to hold C-c down
too long, sending two of them, and, more importantly, also
"C-c C-c runs the command w3m-form-input-textarea-set", so it is easy
to get disoriented and ... "Poof, I have just submitted the form! Agggg".
I just did this by accident editing a Wikipedia article. Good thing it
wasn't anything really important, like submit a message to Santa Claus.
Indeed, four C-c's will blast one direct from the *w3m form textarea*
to already having submitted the form before one has the chance to
remove one's fat fingers from the keyboard and reach for the Geritol.

In gnus I am very happy with
(defun jidanni-message-confirm ()
  "Confirm that we really want to send the message."
  (interactive)(or (y-or-n-p "Send?")(keyboard-quit)))
(add-hook 'message-send-hook 'jidanni-message-confirm)
But I don't see such a hook in w3m-submit-form.
I would unbind C-c C-c but it does seem convenient sometimes, now that
I stumbled upon it.

Maybe add a variable w3m-submit-form-safety-check that asks y or n.