Widespread changes throughout Moodle to make sure it works on

Widespread changes throughout Moodle to make sure it works on
servers that have register_globals turned off (this is the
default setting on newer version of PHP).

In fact it's partly a hack that globalises all GET, POST, FILES
AND COOKIE variables.  Unfortunately though the SESSION and
USER global session variables are only available as $_SESSION["USER"]
and $_SESSION["SESSION"], which is cumbersome to use.

So, for every request I now make a copy of these two session variables
into $USER and $SESSION.  Whenever I update them thoughout Moodle I
now have to call save_session("USER") which copies them back to the
session variable.  This seems to be working well now.

Because I'm using $_SESSION etc now this will raise
the required minimum version of PHP to 4.1.0