Document new dictionary equality predicate.

doc/utils.md

@@ -138,6 +138,16 @@ Performs a reduce operation on the pairs of given dictionary using
 accept three arguments: the value accumulated so far, the key and the
 value.
 
+    (ldict-equal? d1 d2 [equality?])
+
+* ```d1``` - a ldict instance
+* ```d2``` - a ldict instance
+* ```equality?``` - optional equality? predicate for values
+
+Returns ```#t``` if both dictionaries contain the same keys and their
+values are equal according to the provided ```equality?``` predicate
+which defaults to ```equal?```.
+
 ### Format
 
     (import util-format)