Allow Firefox to log in securely from unsecure HTTP://reddit.com

This is necessary because Firefox treats requests from HTTP --> HTTPS
on the same domain as a cross-site request and blocks cookies from it
unless the withCredentials flag is set on the call.

See https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS#Requests_with_credentials

This does *not* fix the issue for Opera, although adding a similar line
to the Opera code will probably work.
make accountSwitcher.js send an isLogin flag

This is necessary so that we can set a CORS
withCredentials flag on the AJAX call, otherwise
some browsers (Firefix, apparently Opera) will
block the cookies if we try to log in from
unsecure http://reddit.com.