Revert "Revert fb444507 which is no longer necessary with the release of Opera 11. Fixes #7608." We will be continuing to support Opera 10.6 in jQuery 1.5.

This reverts commit 012f0c3b.

Avoid running jQuery.unique() for methods that are guaranteed to produce a unique result set. Fixes #7964 - Some traversal methods perform an unnecessary uniqueness check.

Moved jQuery.ajax.prefilter and jQuery.ajax.transport to jQuery.ajaxPrefilter and jQuery.ajaxTransport so that proxying the ajax method doesn't turn into a nightmare. Thanks go to scott_gonzalez and DaveMethvin for pointing out the issue. Also made ajaxSetup return "this" to enable chainable definitions -- jQuery.ajaxSetup(...).ajaxPrefilter(...).ajaxTransport(...).

Fixes #4964. Adds a statusCode object together with a new statusCode method on the jXHR object (deferred behaviour). They accept a map of statusCode/callback(s). Callbacks are fired when the status code of the response correponds to the key (as a success or an error callback depending on how the request completed). Unit tests added.

Removed xhr pooling since failing cross-domain requests leaves the xhr object in an undefined state in Firefox. Also rewrote comments related to the active xhr list so that they make sense.

Reworked script and xhr abort logic to take advantage of the fact jXHR.abort will complete the request itself if not done already.

Fixes #4897. Added ?? as a context-insensitive placeholder for the callback name of a JSONP request. Unit tests provided.

Fixes #6230. Added a unit test to control that, since the ajax rewrite, setting the Accept header actually replaced the previous value and didn't append to it (tested in Safari 4.0.4 for which the problem was specifically reported).

Fixes 4825. jQuery.fn.load: use the jXHR's Promise interface to get the actual response in case ajaxSettings contains a dataFilter. Unit test added.

Ensure that buildFragment clones elements properly in all browsers. Fixes #3879, #6655. Also improves form element clone tests and fixes bugs in $.fn.clone exposed by these new test cases related to the values of checkboxes and radio buttons in IE.

Revert fb444507 which is no longer necessary with the release of Opera 11. Fixes #7608.

Ensure that the DOM element ref in an event handler is removed by cleanData to avoid an IE6/7/8 memory leak. Fixes #7054.

Fixes #5803. Reworked jsonp prefilter so that it sets the dataType as jsonp and recognizes requests with originalSettings having jsonp or jsonpCallback to be jsonp. Moved default jsonp option value into ajaxSettings. Attached the transport to "jsonp" which avoids unnecessary testing. Transport factory sets dataType back to json for proper data conversion.

Fixes #5955. Option crossDomain now forces ajax to consider a request as cross-domain even when it is not. Useful for when servers issue redirects to cross-domain urls. Unit test added.

Make sure prefilters have been called and transport has been selected before sending any global event (in case the "global" option has been changed).

Added a test for retrying a request on error using jQuery.ajax(this). Works as intended. Fixes #7461.

Fixes #7465. Reworked the regexp and associated test for cross-domain detection so that it now includes ports. Added cross-domain detection tests for protocol, hostname and port.

Fixes #7881. Setting contentType to false will prevent the Content-Type header from being sent. Unit test added.