browser compatibility changes for prototype-ujs

The attached patch works around the following problems in the prototype rails.js:

• Element.findElement("a[data-remote]") etc. didn't work in Konqueror. It seems not to return; didn't investigate further. My workaround is to check whether the current element is a anchor and has data-xxx set. This makes more sense anyway, because I cannot think of a use case where we would take the url of a parent element instead of the one that triggered the click event.
• The submit event doesn't bubble in IE (as was already noted in a comment). I've worked around this by observing the click event of the form's submit button instead (which is also fired when the button is pressed via keyboard).

Tested in FF 3.6, Konqueror 4.4.0, IE 8 (normal and in compat mode).