Do not backup / restore flag singletons.

The reload backup process would back up singletons, but not functions
and methods that used those singletons as default arguments. The
result was that the singletons would change identity, but not
the default arguments - and the code using them would fail in
odd ways.

An example problem this caused is
http://lemmasoft.renai.us/forums/viewtopic.php?p=320775#p320757 .