If there were outdated savefiles encountered during
startup, each individual one was getting a wait_synch
that required a <return> even though a message window
wasn't being used at that point.
Allow suppression of the individual per-file wait_synch()
calls on Windows, so that a single one can be done once
the selectsave processing is overwith.
This was a little messy because an indicator had to flow
down through validate(), uptodate(), etc.
There shouldn't be any change in how things behave on
any non-Windows platforms.
14faa682c4