Function: plotexport
Section: graphic
C-Name: plotexport
Prototype: GGD0,L,
Help: plotexport(fmt,list,{flag=0}): draw vector of rectwindows list as
 in plotdraw, returning the resulting picture as a character string;
 fmt is either "ps" or "svg".
Doc: draw list of rectwindows as in \kbd{plotdraw(list,flag)}, returning
 the resulting picture as a character string which can then be written to
 a file. The format \kbd{fmt} is either \kbd{"ps"} (PostScript output)
 or \kbd{"svg"} (Scalable Vector Graphics).

 \bprog
  ? plotinit(0, 100, 100);
  ? plotbox(0, 50, 50);
  ? plotcolor(0, 2);
  ? plotbox(0, 30, 30);
  ? plotdraw(0); \\ watch result on screen
  ? s = plotexport("svg", 0);
  ? write("graph.svg", s); \\ dump result to file
 @eprog
