Fix failing build in XCode 8.3 (#3241)

Source/AsyncDisplayKit.modulemap

@@ -0,0 +1,19 @@
+framework module AsyncDisplayKit {
+  umbrella header "AsyncDisplayKit.h"
+  
+  export *
+  module * {
+    export *
+  }
+  
+  explicit module ASControlNode_Subclasses {
+    header "ASControlNode+Subclasses.h"
+    export *
+  }
+  
+  explicit module ASDisplayNode_Subclasses {
+    header "ASDisplayNode+Subclasses.h"
+    export *
+  }
+  
+}