SPI_cursor_move — move a cursor
void SPI_cursor_move(Portalportal, boolforward, longcount)
   SPI_cursor_move skips over some number of rows
   in a cursor.  This is equivalent to a subset of the SQL command
   MOVE (see SPI_scroll_cursor_move
   for more functionality).
  
Portal portalportal containing the cursor
bool forwardtrue for move forward, false for move backward
long countmaximum number of rows to move
   Moving backward may fail if the cursor's plan was not created
   with the CURSOR_OPT_SCROLL option.