[XeTeX] Asymptote support xetex engine issue.

[yunhual]

I have also check the latex engine how to work with asymptote.
asymptote first transfer all to a dvi file. then call dvips to transfer
dvi file to ps file. and dvips can adjust the the origin coordinate by
pass -O x, y to it. for our example. like this:
dvips -R -Pdownload35 -D600 -O 134.58bp,228.18bp -T 612bp,792bp  -q -o
test.ps test_.dvi
while the -O 134.58bp,228.18bp are new X and Y coordinate, so every
things is right.

But it is seem that we can not do same job in xdvpdfmx. I have tried the
-x and -y paramate of xdvpdfmx. it can use new origin coordinate. but
xdvpdfmx first call gs to produce test_0.eps to test_0.pdf(the picture
of the circle). the third and fourth quadrants of the circle has been
lost. so it got wrong.
so we must find a method to let gs use new origin coordinate.
thank you.