Fix for a selector speed regression (calling a simple selector many times resulted...

Fix for a selector speed regression (calling a simple selector many times resulted in a significant speed down). This has been fixed by breaking the RegExps out into the global scope. This required that a closure be implemented around the full jQuery script (which is now the case). Some simple changes were made in addition to the RegExp one, allowing for some greater flexibility on our part - and hopefully better compression.

Speed results:
http://dev.jquery.com/~john/ticket/1351/ vs.
http://dev.jquery.com/~john/ticket/1351/113.html vs.
http://dev.jquery.com/~john/ticket/1351/112.html