Restrict onunload removal of eventhandlers to IE and Firefox 2

[JeroenH]

In event.js the last lines remove registered eventhandlers on unload in all browsers. This is needed for IE's memory leaks and initially only targeted IE. In ​#1911 this was changed to apply to all browsers, but the only other browser in need of a fix there was Firefox 2.

This change breaks fast history navigation in Opera (and ​also in Firefox).

When testing the testcase in #1911, I can reproduce the problem in FF2, but it does not appear anymore in FF3.

It would be better to restrict this change to the browsers that need the fix:

// Prevent memory leaks in IE
// And prevent errors on refresh with events like mouseover in mozilla < 1.9
// Window isn't included so as not to unbind existing unload events
if (jQuery.browser.msie || (jQuery.browser.mozilla && parseFloat(jQuery.browser.version) < 1.9) ){
	jQuery(window).bind("unload", function() {
		jQuery("*").add(document).unbind();
	});
}

[JeroenH]

This got fixed somewhere, by adding conditional comments for IE.

[sylvain]

This was fixed in ticket:5198 (changeset:6551).