fix for #3533, triggering an event with a colon in the name on a table no longer throws an error in IE

Adding support for etags in $.ajax() - and simplified the if-modified-since implementation. Thanks to Lawrence for the patch! Closes ticket #4764.

jquery core: removed the version.txt newline; please keep it that way, otherwise that ant replacement fails, it inserts the file content wherever it finds @VERSION

Switched to using new Function instead of eval for handling JSON parsing (Fixes bug #4680). Added support for JSON.parse, if it exists (Fixes bug #4429).

Did some light reordering of the jQuery definition. Moved window and undefined to exist in intro/outro.

fix remove and empty to work properly in IE when an element with the id of length exists. fixes ajax event hanlders in test suite from firing multiple times because they did not get cleaned up.

.bind() now accepts an optional thisObject as the last argument which is used to change the value of this in event callbacks. fixes #3699

fix :hidden selector that was accidentally reverted in previous commit, also fixed tests for :hidden selector in IE6

make sure toggleClass does not delete classNames when forcefully removing classes and they are already removed