improved (?) header markup and styles.
Other misc changes.

big change to session handling when user not logged in.  Now, behaves as Drupal normally would without cookies.  No session across multiple requests.

fix for ?destination=... parameters
other misc fixes.

Big changes to user data (cleaned up problem where too much was being stored there).  Fixes problem where bogus fbu in user data was screwing things up.  Also keeps the authmap table properly in sync, by forcing updates with every new session.  Hopefully these changes don't break too much.

Minor tweaks.  Fixed problem where hook_fb(FB_OP_APP_IS_AUTHORIZED, ...) was being called too many times on a single page.

#694048; removed deprecated block.  Also, moved drupal_goto() call from fb_user.module to fb_canvas.module (because it applies only to canvas pages and had fb_canvas specific code).

set uid to NULL rather than 0 when uid is not known.

Change to authmap logic.  Set authmap more frequently, do avoid a tricky situation when the user object has an fbu, but the authmap has not been set.