fixes: #1166272 by Dave Cohen, John Klehm: support for facebooks oauth 2.  Mostly an upgrade of fixes from 6.x branch.

changed 'fb_session_no' to 'fb_session_handoff'
changed order of javascript event handling, hope to avoid bogus session change events.

numerous changes, especially to session management and url rewriting. performance improvements and code simplification.

#614260; at least partial fix.  resolves issues with iframe support in fb_fbml theme and infinite redirect when fb_connect and iframes used together.

Moved pseudo-event subscription to init function, not drupal behavior.

Added concept of pseudo-events to allow easier customization of javascript behavior.

Added theme hooks to build serverfbml from data structures.

Use cache to store init javascript, because session is not shared with facebook event callbacks.

Changes to fbConnect session management.  Changing session id when logged in via fb connect.  This prevents the Drupal session from conflicting with the fbconnect session, and ensures user is properly logged out when user logs out of facebook.

very little testing, may be buggy