Added docs for the legend sorted option.

API.txt

@@ -141,6 +141,7 @@ Customizing the legend
     backgroundColor: null or color
     backgroundOpacity: number between 0 and 1
     container: null or jQuery object/DOM element/jQuery expression
+    sorted: null/false, true, "ascending", "descending" or a comparator
   }
 
 The legend is generated as a table with the data series labels and
@@ -167,6 +168,21 @@ specify "container" as a jQuery object/expression to put the legend
 table into. The "position" and "margin" etc. options will then be
 ignored. Note that Flot will overwrite the contents of the container.
 
+Legend entries appear in the same order as their series by default. To
+sort them alphabetically, you can specify "sorted" as tue, "ascending"
+or "descending", where true and "ascending" are equivalent.
+
+You can also provide your own comparator function that accepts two
+objects with "label" and "color" properties, and returns zero if they
+are equal, a positive value if the first is greater than the second,
+and a negative value if the first is less than the second.
+
+  sorted: function(a, b) {
+    // sort alphabetically in ascending order
+    return a.label == b.label ? 0 : (
+      a.label > b.label ? 1 : -1
+    )
+  }
 
 Customizing the axes
 ====================