Return a list of strings as a set of arranged in columns.

Each column is only as wide as necessary. By default, columns are separated by two spaces - one was not legible enough. Set "colsep" to adjust the string separate columns. Set `displaywidth' to set the line width.

Normally, consecutive items go down from the top to bottom from the left-most column to the right-most. If +arrange_vertical+ is set false, consecutive items will go across, left to right, top to bottom.