This change allows the vsv.c extension to read EITHER a plain-text file, OR a gzipped plain-text file as the filename= parameter automagically. If you have a file called `THEFILE.CSV` then you can gzip that file using the command `gzip THEFILE.CSV` which will create a file called `THEFILE.CSV.gz` See <https://en.wikipedia.org/wiki/Gzip> For a file that is about 32 MB, the GZipped stream is about 5 MB.