Removed hack intended to manage %user_uid_optional case; turns out that the to_arg function on the menu item handled it all for us, and it's unnecessary by the time we get to Panels.

#307628: Fixed creation of $panel_args in the panel_page menu handling system to contain raw id values, as expected by views and node content for string substitution.

Updated context callback to comply with changes stemming from the D6 menu system. (Can handle both a uid and a fully-loaded user object, now)

#311192: Significant refactoring of the menu system; arguments at various non-override paths should now be operational, along with some other intelligent additions to the system.

Initial D6 work -- this includes only panels.module stuff. Right now the drag & drop display editor works, layout, layout settings and render works. Special features such as cache and styles may or may not work.