that the global `sesslist' got out of sync with the saved-sessions submenu,
causing the latter to launch the wrong sessions.
Also, Change Settings wasn't getting a fresh session list, so if the set of
sessions had changed since session startup it wouldn't reflect that (at least
until a session was saved). Fixed (on all platforms).
Therefore, since the global sesslist didn't seem to be useful, I've got rid
of it; config.c creates one as needed, as do the frontends. (Not tried
compiling Mac changes.)
Also, we now build the saved-sessions submenu on demand on Windows and Unix.
(This should probably also be done on the Mac.)
[originally from svn r5609]