0) Update descriptions of symbol-file, file, add-symbol-file cmds for use

0) Update descriptions of symbol-file, file, add-symbol-file cmds for use
of *options* "-readnow" and "-mapped".

1) Change title/subtitle to come closer to text used by FSF when they
printed this thing (but still avoid silliness of having word "manual" in
the title).

2) First few minor corrections from most recent Chassell pass.