Port jQuery Update to 6.x

This patch basically represents a complete re-write of the entire module. 6.x rocks.

- removes compat.js
- removes misc/ directory and all files under that.
- removes ALL of the code in jquery_update.module and replaces it with a single, ~10-line function: jquery_update_preprocess_page().
- adds the 1.2.4a version of jQuery that comes with jQuery UI (which is not actually 1.2.4a... it's some nightly build from around then). It is NOT the packed version, but will be replaced with the packed version when 1.2.4 "proper" gets released.
- rewrote README.txt

Oh, nevermind. I compiled a packed version of 1.2.4b from http://jqueryjs.googlecode.com/svn/tags/1.2.4b/. 'ant pack' ftw!

Hrm. jjeff pointed out that if a theme has the following in *its* theme_preprocess_page()...

$vars['scripts'] = drupal_get_js();

that it's going to undo the magic we have going on here. Phooey. Going to try a neat trick he came up with with theme_registry_alter.

Ok, this gets around the problem, by forcing jquery_update's preprocess_page function to the end of the stack.

and you know, if I'm going to do that, this module should probably be weight 99 so that no module called "kaka" calls does this hook_theme_registry_alter() trick and then $vars['scripts'] = drupal_get_js(); in *its* preprocess_page function. :P

Actually, I need something different. I need a weird version of jQuery that works with jQuery UI (1.2.4 "proper" doesn't). So I need to re-work this module so that you can select from a settings page which version of jQuery to load.

Don't ask me, I just have to get it working. :P Good luck getting 1.2.4 into core.

Actually, I think selection is taking it too far, and I've already spent /way/ more time on this than I probably should have. ;)

Committed the attached to HEAD. Will leave it there for awhile for people to test, and probably branch and release once jQuery UI comes out of beta and we can use a 'proper' version of jQuery.

Incidentally, read the README.txt. You no longer have to replace the core jquery.js to use this module, thanks to page preprocess hooks and hook_theme_registry_alter(). Yippee!