Change GE and GST to change top-level defaults only if in the

Change GE and GST to change top-level defaults only if in the
top-level REPL.  Eliminate VE, VST, %GE, %VE, %GST, %VST, %IN, %OUT.
Change RE to clobber the reader history with the thing it is
re-evaluating.  Change prompt-for-confirmation to print out invalid
characters.