Add docstring and :added metadata to definterface.

Signed-off-by: Stuart Halloway <stu@thinkrelevance.com>

src/clj/clojure/core_deftype.clj

@@ -36,7 +36,15 @@ ditto for method impls defined with deftype, defrecord, and reify."))))
             "No varargs nor destructuring support for definterface and defprotocol method sigs."))))
 
 ;for now, built on gen-interface
-(defmacro definterface 
+(defmacro definterface
+  "Creates a new Java interface with the given name and method sigs.
+  The method return types and parameter types may be specified with type hints,
+  defaulting to Object if omitted.
+
+  (definterface MyInterface
+    (^int method1 [x])
+    (^Bar method2 [^Baz b ^Quux q]))"
+  {:added "1.2"} ;; Present since 1.2, but made public in 1.5.
   [name & sigs]
   (let [tag (fn [x] (or (:tag (meta x)) Object))
         psig (fn [[name [& args]]]