[ESS] patch to ess-swv.el

[Richard M. Heiberger]

On Windows using MikTeX, the standard is

dvips -t letter filename.dvi > filename.ps
ps2pdf filename.ps filename.pdf

the dvi viewer is
yap.exe

the windows ghostview viewer is
GSview32.exe

the adobe viewer is
AcroRd32.exe


In the dvips line above, the "-t letter" is necessary in the United
States to get the output file sized correctly for letter paper.
The default is A4 paper which is slightly longer and narrower.  Files
sized for A4 paper look terrible on letter paper (and probably viceversa).
This probably means that the papersize needs to be a customization
option.  Maybe the default should be sensitive to locale.

Again on Windows, most systems are set so the .dvi, .ps, and .pdf extensions
automatically find the right program.  You need something based on
    (w32-shell-execute nil filename)
to take advantage of those settings.

Rich