A text file is created with the specified name. The supplied
comment is written to the file as the first record (so long as it
is not blank), using the groups current comment character (see
routine GRP_SETCC). All the names stored within the specified
group section are then written to the file, one name per record.
If the group is case insensitive (as set up by a call to routine
GRP_SETCS) then the names are written out in upper case,
otherwise they are written out as supplied.
The routine GRP_LIST can be used if the file name is to be
obtained through the parameter system.