Stores jQuery.ajaxSettings.isLocal locally at load time so that any change to it...

Stores jQuery.ajaxSettings.isLocal locally at load time so that any change to it won't affect the transport. Fixes the url parsing regexp to deal with empty domains. Adds informative text into test/localfile.html and handles Opera's failure. Revises the way xhr are created by doing all tests at load time and normalizes all the xhr creation functions so that none of them may throw an exception.