CLJS-1246: Add cljs.core/record? predicate.

Author: brandonbloom

src/cljs/cljs/core.cljs

@@ -1783,6 +1783,11 @@ reduces them without incurring seq initialization"
     false
     (satisfies? IMap x)))
 
+(defn ^boolean record?
+  "Return true if x satisfies IRecord"
+  [x]
+  (satisfies? IRecord x))
+
 (defn ^boolean vector?
   "Return true if x satisfies IVector"
   [x] (satisfies? IVector x))

test/cljs/cljs/core_test.cljs

@@ -1735,6 +1735,8 @@
         letters (C. "a" "b" "c")
         more-letters (assoc letters :d "d" :e "e" :f "f")]
     (testing "Testing records"
+      (is (record? fred))
+      (is (not (record? {})))
       (is (= (:firstname fred) "Fred"))
       (is (= fred fred-too))
       (is (false? (= fred nil)))