search for: auto_save_interval

I'm just about to put an autosave feature into R as per requests by Peter and Kurt. My current thinking is that it should be an option so that it is setable (in the profile if you want). One simply specifies the number of commands that are executed between calls to save. It won't be incremental; I'll just dump the output of ls(). I think that the file name should not be .RData but