Extend the docs for Data.List.transpose

by giving a sufficient general example to explain what happens when the
rows are not of the same lengths. Thanks to Doug McIlroy for the
suggestoin. Fixes #10128.

libraries/base/Data/OldList.hs

@@ -468,6 +468,10 @@ intercalate xs xss = concat (intersperse xs xss)
 -- For example,
 --
 -- > transpose [[1,2,3],[4,5,6]] == [[1,4],[2,5],[3,6]]
+--
+-- If some of the rows are shorter than the following rows, their elements are skipped:
+--
+-- > transpose [[10,11],[20],[],[30,31,32]] == [[10,20,30],[11,31],[32]]
 
 transpose               :: [[a]] -> [[a]]
 transpose []             = []