A change to the default GS distilling command due to a deprecation warning

FYI, for the upcoming XPP 9.6.0 release the default Ghostscript (GS) distilling command that XPP runs has been changed due to a deprecated warning being output by GS.

Situation: With the 9.4.0 release, we incorporated version 9.50 of GS into XPP.

It only became apparent recently, when one of us happened to manually run a GS distilling command on a PS file (while working on a bug fix in PS being generated for table rules), that when running the current (documented) default GS distilling command (XYV_EXECS/gs/gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=input.pdf -c .setpdfwrite -f input.ps), that you see the following warning:

**** WARNING: The .setpdfwrite operator has been deprecated and will be removed entirely
              in the next release of Ghostscript. The functionality of this operator has
              been reduced to increasing the size of the VM threshold. If you believe you
              have a real need for this then you should replace your call to .setpdfwrite
              with:
                  3000000 setvmthreshold

We didn't realize this was happening because you do not see this warning when running a GS distill with the psfmtdrv program; you only see it when manually running a GS distilling command.

With the 9.6.0 release, the default GS distilling command used by XPP has been changed to: XYV_EXECS/gs/gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=input.pdf -c currentuserparams /VMThreshold get 3000000 .max setvmthreshold -f input.ps

Thus replacing the reference to the deprecated .setpdfwrite operator in the command with what it actually does. The documentation of this default command has also been changed for the upcoming 9.6.0 release (in the PDF Support in XPP manual).

Since this is only a warning, we only made these changes for XPP 9.6, but if you are manually running GS distilling commands (and are using XPP 9.4/9.5) and find this warning message annoying you can make the same change to the GS command that you are running.