Write a tab delimited text file. The first row should
contain the field names for a structure. Each following
row contains the data for one instance of that structure.
This routine writes each element of the structure array as a row.
Only numeric and string field values are supported.
If the filename is a string, this routine handles opening and
closing of the file. Otherwise, this routine assumes
that what was passed is a valid fid and uses it as such,
leaving the calling routine to do the opening and closing.
06/16/03 dhb Wrote it.
07/01/03 dhb Support string fields too.
08/12/06 dhb Call filetype only if OS9.
07/07/13 dhb Add handling of non-string filename as fid.